USOO8981.211 B2

(12) United States Patent (10) Patent No.: US 8,981.211 B2 Girt et al. 45) Date of Patent: Mar. 17,9 2015

(54) INTERLAYER DESIGN FOR EPITAXIAL (58) Field of Classification Search GROWTH OF SEMCONDUCTORLAYERS CPC ...... H01L 21/02488; HO1L 21/02491; H01L 21/02505; H01L 21/02513; H01L (75) Inventors: Erol Girt, San Jose, CA (US); Mariana 21/02516; H01L 31/03682: H01L 31/0392: Rodica Munteanu, Santa Clara, CA H01L 31/068; H01L 31/1872 (US) USPC ...... 136/258, 256; 257/77, E21.061, 257/E29.104; 438/660, 694 (73) Assignee: Zetta Research and Development See application file for complete search history. LLC-AQT Series, Wilmington, DE (US) (56) References Cited (*) Notice: Subject to any disclaimer, the term of this U.S. PATENT DOCUMENTS patent is extended or adjusted under 35 U.S.C. 154(b) by 1457 days. 8,148,631 B2 * 4/2012 Fix et al...... 136,262 2005, 0087225 A1 * 4, 2005 Morooka et al...... 136,256 (21) Appl. No.: 12/405,963 2005. O139252 A1* 6, 2005 Shim ...... 136,244 2007/004.4832 A1* 3, 2007 Fritzemeie ... 136,252 1-1. 2007. O159065 A1* 7, 2007 Yan et al...... 313,503 (22) Filed: Mar 17, 2009 2007/0224453 A1* 9, 2007 Inamura et al...... 428,827 O O 2008/0078444 A1* 4/2008 Atanackovic ...... 136,256 (65) Prior Publication Data 2008. O105299 A1* 5, 2008 Krasnov ...... 136,256 US 2009/O235983 A1 Sep. 24, 2009 2008/0216891 A1 ck 9/2008 Harkness et al...... 136,256 * cited by examiner Related U.S. Application Data (60) Provisional application No. 61/037,571, filed on Mar. Primary Examiner — Matthew Martin 18, 2008. (74) Attorney, Agent, or Firm — Mattingly & Malur, PC (51) Int. Cl. (57) ABSTRACT HOIL 3L/ (2006.01) HOIL 21/02 (2006.01) An interlayer structure that, in one implementation, includes HOIL 3L/0368 (2006.01) a combination of an amorphous or nano-crystalline seed HOIL 3L/0392 (2006.01) layer, and one or more metallic layers, deposited on the seed HOIL 3L/068 (2012.01) layer, with the ficc, hop or bcc is used to HOIL 3L/8 (2006.01) epitaxially orient a layer on top of non-single (52) U.S. Cl. crystal Substrates. In some implementations, this interlayer CPC. H0IL 21/02521 (2013.01); HOIL 21/02488 structure is used to establish epitaxial growth of multiple (2013.01); HOIL 21/02491 (2013.01); HOIL semiconductor layers, combinations of semiconductor and 21/02505 (2013.01); HOIL 21/02513 (2013.01); oxide layers, combinations of semiconductor and metal lay HOIL 21/02516 (2013.01); HOIL31/03682 ers and combination of semiconductor, oxide and metal lay (2013.01); HOIL 31/0392 (2013.01); HOIL ers. This interlayer structure can also be used for epitaxial 31/068 (2013.01); HOIL 31/1872 (2013.01); growth of p-type and n-type in photovoltaic Y02E 10/546 (2013.01); Y02E 10/547 (2013.01) cells. USPC ...... 136/258: 136/256; 438/660; 438/694; 257/77; 257/E21.061; 257/E29.104 34 Claims, 18 Drawing Sheets

111) (111) 111) A 4

Growth direction

A 111) A111A 111111 N V U.S. Patent Mar. 17, 2015 Sheet 1 of 18 US 8,981.211 B2

111) (111) 111 A -.

Fig. 1A Growth direction

A (111A111A (111111 N \

Fig. 1B U.S. Patent Mar. 17, 2015 Sheet 2 of 18 US 8,981.211 B2

Imaginary plane formed by incident and reflected X-ray beams Incident / Reflected X-ray beam X-ray beam

Deposited layers

Fig. 2 U.S. Patent Mar. 17, 2015 Sheet 3 of 18 US 8,981.211 B2

1.OE--O4. wSeed layer/Au/Heat? Si 0-20 Scan

A. O E -- O 3 Au 111 2.OE--O3 l Au 200 Au 220 Au 311

Y^ss S OOE--OO

OE--O3

OOE--OO U.S. Patent Mar. 17, 2015 Sheet 4 of 18 US 8,981.211 B2

eat, i

0-20 Scan

1 CE--C3 YsS. 5 OE--O2 N

?ö. Fig. 4a

1O 15 35 Fig. 4b U.S. Patent Mar. 17, 2015 Sheet 5 of 18 US 8,981.211 B2

1. E+05

1 - i i is 8.E+O4 0-20 Scan 6.E+04

4.E+04 eSeed layer/Au/Heat/Mo/Si 2.E+04 Au 111 O E -- O O s cassessssss sississsssssssssssssssssssssssssssssssss

25 35 45 55 65 AD 35 26 degree Fig. 5a

12E--O5 YSeed layer/Au/Heat/Mo/Si 1.OE--O5

S.

S.S S 8 OE--O4 S S.S SŠ S 6 OE--O4. ŠS SS SSS S S SSS. SS. -- s S 4. O O A. SSS S

& w O O E -- O O www.s' YawSSSSssssssssss WWSSS w 5 1O 15 2O 25 G degree Fig. 5b U.S. Patent Mar. 17, 2015 Sheet 6 of 18 US 8,981.211 B2

Semiconductor layers

U.S. Patent Mar. 17, 2015 Sheet 7 of 18 US 8,981.211 B2

< Semiconductor layers

U.S. Patent Mar. 17, 2015 Sheet 8 of 18 US 8,981.211 B2

6 Underlayer1. foc or boc or hop

<- Seed layer Amorphous or nanocrystalline Fig. 10

6 Underlayer2 foc or boc or hop

Underlayer1. -C- foc or boc or hop

<- Seed layer Amorphous or nanocrystalline Fig. 11 U.S. Patent Mar. 17, 2015 Sheet 9 of 18 US 8,981.211 B2

U.S. Patent Mar. 17, 2015 Sheet 10 of 18 US 8,981.211 B2

U.S. Patent Mar. 17, 2015 Sheet 11 of 18 US 8,981.211 B2

Fig. 14a

Fig. 14b (-Semiconductor layers

U.S. Patent Mar. 17, 2015 Sheet 12 of 18 US 8,981.211 B2

3. sy bcc underlayer growth directions

Fig. 14d

€ Semiconductor layers

::::::::::::: bcc underlayer < <110> growth directions

U.S. Patent Mar. 17, 2015 Sheet 13 of 18 US 8,981.211 B2

Fig. 14f

U.S. Patent Mar. 17, 2015 Sheet 14 of 18 US 8,981.211 B2

s s sy foc underlayer 3. <111> growth directions

€ Semiconductor layers

:::::: foc underlayer U.S. Patent Mar. 17, 2015 Sheet 15 of 18 US 8,981.211 B2

(-Semiconductor layers

Fig. 14.j

U.S. Patent Mar. 17, 2015 Sheet 16 of 18 US 8,981.211 B2

-CH UnderlayerN (NS100) foc, boc or hop

Underlayer3 losely,

Underlayer4 foc or boc or hop

€ Underlayer3 foc or boc or hop

-(- Underlayer2 foc or boc or hop

Underlayer1. (CH foc or boc or hop

C - Seed layer Amorphous or nanocrystalline Fig. 14L U.S. Patent Mar. 17, 2015 Sheet 17 of 18 US 8,981.211 B2

<- Top Contact layers

<- n-type semiconductor layer

Underlayer4 foc or boc or hop

€ Underlayer3 foc or boc or hop

Underlayer2

foc or boc or hop

::::::: Underlayer1. foc or boc or hop

C - Seed layer Amorphous or nanocrystalline Fig. 15 U.S. Patent Mar. 17, 2015 Sheet 18 of 18 US 8,981.211 B2

US 8,981,211 B2 1. 2 INTERLAYER DESIGN FOR EPITAXIAL FIG. 2 illustrates example measurement geometries for GROWTH OF SEMCONDUCTORLAYERS X-ray structural characterization of deposited layers. FIGS. 3a, 3b, 4a, 4b, 5a, and 5b are plots illustrating the CROSS-REFERENCE TO RELATED results of 0-20 and rocking curve scans of epitaxially grown APPLICATIONS semiconductor layers. FIG. 6 to 13 set forth various example layer structures that The present application claims priority to U.S. Provisional can be used to promote epitaxial growth of a semiconductor Application Ser. No. 61/037,571 filed Mar. 18, 2008, the layer. entirety of which is incorporated by reference herein. FIG. 14a to 141 illustrate example layer structures with TECHNICAL FIELD 10 crystal growth directions. FIG. 15 illustrates example layer structures with epitaxi The present disclosure generally relates to semiconductors ally-grown semiconductor layers that can be used in Solar and to epitaxial growth of semiconductor layers. sells. FIGS. 16a and 16b illustrate example photovoltaic cell BACKGROUND 15 structures according to various implementations of the inven tion The term epitaxy in general describes an ordered crystal line growth of deposited layers. Epitaxial growth of a semi DESCRIPTION OF EXAMPLE EMBODIMENT(S) conductor layer has traditionally been achieved by growing a semiconductor material on top of a single crystal Substrate, Introduction Layer Growth and Characterization where the crystal lattice of the single crystal substrate Ifa deposited layer consists of grains with crystalline struc matches the crystal lattice of the deposited semiconductor ture, each grain can grow along a different growth direction. material. Epitaxial layers may be grown with vapor-phase The growth direction is defined as the crystal growth direction epitaxy (VPE), a modification of chemical vapor deposition of grains in a deposited layer perpendicular to the Substrate (CVD), liquid-phase epitaxy (LPE), and physical vapor depo sition (PVD) (evaporative deposition, electronbeam physical 25 Surface. For example, consider a layer that consists of grains vapor deposition, Sputter deposition, pulse laser deposition, with ficc crystal structure. These grains can grow along a chatodic-arc deposition, and beam physical vapor depo single growth direction (for example 111, as shown in FIG. sition). If a layer is deposited on a Substrate of the same 1b) or along different growth directions (as shown in FIG. composition, the process is called homoepitaxy; otherwise it 1a). If the grains grow along a single growth direction, the is called heteroepitaxy. Epitaxy is used in silicon-based 30 growth is epitaxial and the layer is called an epitaxially manufacturing processes for bipolar junction transistors grown layer. Otherwise, if grains grow along different growth (BJTs) and modern complementary metal-oxide-semicon directions (see FIG. 1a, where 111 crystal direction of ductor (CMOS). Epitaxy is also used in production of laser grains is oriented along different directions) the growth is emitting diodes (LEDs) and in solar cells. random. 35 Crystal growth directions 111, -111, 1-11, 11-1, SUMMARY -1-11, 1-1-1, -11-1, and I-1-1-1 are equivalent and collectively are referred to as <111 > directions. In the follow The present invention involves the epitaxial growth of ing text, the notation <111 > refers to all equivalent 111 semiconductor layers on a Substrate alternative to single crys directions, <0001 > for all equivalent 0001 directions, and tal substrates that involves the use of a metallic interlayer 40 <110> for all equivalent 110 directions. having a closed-packed crystal structure. The following dis The structural characterization of deposited layers may be closure demonstrates how an epitaxial semiconductor layer carried out by X-ray diffraction (XRD) using 0-20 and rock can be grown on a glass, metal or plastic Substrate. The ing curve scans. Measurement geometry is described in FIG. disclosed invention and embodiments can be used to obviate 2. In a 0-20 Scan, the angle between an incident X-ray beam the need for expensive single crystal Substrates traditionally 45 and the Substrate surface, 01, is the same as the angle between used to epitaxially grow semiconductor layers. In a particular the reflected X-ray beam and the substrate surface, 02, implementation, this is achieved by deposition of an inter (01–02=0). In the rocking curve scan, the angle between the layer, which includes an amorphous or nano-crystalline seed incident and reflected beams, 03, is kept constant (i.e., 01+02 layer and one or more metallic layers with a close-packed is kept constant) and the sample is rocked by angle (), so that crystal structure (e.g., face center cubic (fcc), hexagonal 50 the angle between the incident X-ray beam and the substrate, close-packed (hcp) or body center cubic (bcc)), on a substrate 01, varies(180-03)/2-()/2 to (180-03)/2+(i)/2. In both mea prior to Sputtering a semiconductor layer. In a particular Surements, the imaginary plane formed by incident and dif implementation, the metallic layers with a close-packed crys fracted X-ray beams, see FIG. 2, is perpendicular to the tal structure are polycrystalline with the majority of crystals substrate surface. The 0-20 scan can be used to detect the growing preferentially along a single crystal growth direc 55 growth direction of grains in the deposited layer—i.e., crystal tion. This induces an ordered crystalline growth of grains in growth direction of grains in a deposited layer perpendicular semiconductor layers on top of the interlayer structure. In one to the Substrate surface. The rocking curve scan can be used to implementation, these epitaxially grown semiconductor lay determine the degree of alignment of the growth directions of ers can be used in Solar cells. For example, this interlayer grains with the direction normal to the substrate surface in the structure can also be used for epitaxial growth of p-type and 60 layer. The measure of alignment between the growth direc n-type semiconductors in photovoltaic cells. tions of grains in the layer is often expressed as the full width at half maximum (FWHM) of the peak obtained as a result of DESCRIPTION OF THE DRAWINGS the rocking curve Scan. This peak is narrow for a high degree of alignment between the growth directions of grains in the FIGS 1a and 1 billustrate examples of random and epitaxial 65 layer and is wide for a low degree of alignment between the (respectively) crystal growth direction of grains in a depos growth directions of grains in the layer. Theory predicts ited layer perpendicular to the substrate surface. FWHM of a single crystal on the order of 0.0030 for typical US 8,981,211 B2 3 4 experimental conditions. However, most single crystals also used to increase the grain size of underlayers and semi exhibit FWHM from 0.030 to 0.30. conductors that may be desired in some applications. Experimental Results Example Structures for Promoting Epitaxial Growth We grew a layer structure that includes: 1) an amorphous The following describes various layer structures that can be seed layer, 2) an fecunderlayer formed over the seed layer, used to promote epitaxial growth of a semiconductor layer. and 3) a semiconductor layer formed over the ficc underlayer, FIG. 6 to FIG. 13 illustrate structures that may be used to set all on top of a glass Substrate (glass Substrate/seed layer/fcc epitaxial growth of a semiconductor on top of a non-single underlayer/semiconductor layer). After sputtering the ficc crystal Substrate: underlayer, and before Sputtering the semiconductor layer, 1) Underlayer1/semiconductor layers (FIG. 6); the glass substrate was heated to 300° C. We also grew a layer 10 2) Underlayer1/Underlayer2/semiconductor layers (FIG. structure that includes: 1) an amorphous seed layer, 2) an fec 7); underlayer formed over the seed layer, 3) a bcc underlayer 3) Underlayer1/Underlayer2/Underlayer3/semiconductor formed over the fecunderlayer, and 4) a semiconductor layer layers (FIG. 8): formed over the bcc underlayer. The substrate was heated to 4) Underlayer1/Underlayer2/Underlayer3/Underlayer4/ 300° C. after sputtering the ficc underlayer and before sput 15 semiconductor layers (FIG. 9); tering the bcc underlayer. In this particular experiment, argon, 5) Seed layer/Underlayer1/semiconductor layers (FIG. Ar, was used as the Sputter gas. However, other gases—such 10); as helium (He), neon (Ne), krypton (Kr), Xenon (Xe), nitrogen 6) Seed layer/Underlayer1/Underlayer2/semiconductor (N), oxygen (O) and/or hydrogen (H)—can also be used. layers (FIG. 11): FIG. 3a to FIG. 5b show 0-20 and rocking curve scans 7) Seed layer/Underlayer1/Underlayer2/Underlayer3/ obtained from the following layer structures: 1) Seed layer/ semiconductor layers (FIG. 12); and Au ficc underlayer/Heat/Si semiconductor layer, 2) Seed 8) Seed layer/Underlayer1/Underlayer2/Underlayer3/Un layer/Ni fecunderlayer/Heat/Si semiconductor layer and 3) derlayer4/semiconductor layers (FIG. 13). Seed layer/Au ficc underlayer/Heat/Mobcc underlayer/Si Underlayer1 consists of at least one fec, hep or bcc layer. semiconductor layer. In structure 1) Seed layer/Au/Heat/Si 25 For example, Underlayer1 may include one or more depos and structure 3) Seed layer/Au/Heat/Mo/Si, the grains of the ited layers of an fec, hep or bcc crystal structure. Similarly, Silayer grows along <111 > growth directions. The term Underlayer2 consists of at least one fec, hep or bcc layer. “Heat' in the structures described above refers to the heating Underlayer3 consists of at least one fec, hep or bcc layer. of the substrate to a desired temperature (e.g., 300 C) prior to Underlayer4 consists of at least one fec, hep or bcc layer. depositing a Succeeding layer. The presence of the Molayer 30 Some specific example of structures illustrated in FIG. 6 to 13 between Au and Si in structure 3) Seed layer/Au/Heat/Mo/ with crystal growth directions are shown in FIG. 14a to FIG. Si improves growth of Si grains along <111 > crystal direc 141. Instructures illustrated in FIG. 6 to 13, heat may be used tions. This was deduced from rocking curve scans presented before sputtering Underlayer1. Underlayer2. Underlayer3. in FIG. 1b, and FIG. 3b that show that FWHM of <111 > and/or Underlayer4. In the structures illustrated in FIG. 10 to directions is reduced from 1.1 in structure 1) Seed layer/Au/ 35 13, heat may cause crystallization of an amorphous layer. Heat/Si, to 0.23° instructure 3) Seed layer/Au/Heat/Mo/Si. In This can affect growth of the underlayer on top of the Seed the structure 3) Seed layer/Au/Heat/Mo/Si, the growth layer. To avoid growth of an underlayer on top of an already directions of the Silayer is as good as in some single crystal crystallized Seed layer, at least one underlayer may be depos structures. This shows that this seed layer/underlayer struc ited on top of the Seed layer before heating the substrate. ture can be used to achieve highly directional epitaxial growth 40 Inan fec layer, at least 50% of the grains have an fec crystal of the Silayer. Previously, highly directional epitaxial growth structure. The ficc layer can also consist of at least 50% of has been achieved only by growing Si on top of a single grains with ficc crystal structure Surrounded with an oxide crystal substrate. In structure 2) Seed layer/Ni/Heat/Si. Si grain matrix; in other words, oxide is dispersed at the grain grows along <220> growth directions. The Silayer is also boundaries of the semiconductor fcc grains. U.S. application highly oriented: FWHM of Si <220> is 3.95°. 45 Ser. Nos. 12/016,172, 11/923,036, and 11/923,070 all of In the investigated structures 1) Seed layer/Au/Heat/Si, 2) which are incorporated by reference herein in their entirety Seed layer/Ni/Heat/Si and 3) Seed layer/Au/Heat/Mo/Si, for all purposes, disclose the structure and deposition of one both Au and Ni grow preferentially along <111 > growth or more granular semiconductor and oxide layers with directions, while Mo grows preferentially along the <110> nanometer-size semiconductor grains Surrounded by a matrix direction. FIG. 3a shows that majority of Au grains grow 50 of oxide. These granular semiconductor and oxide layers may along<111 > direction but some of Augrains also grow along be deposited on top of the underlayer structures disclosed <200>, <220> and <311 > directions. In the structure 3) Seed herein. For purpose of improving segregation of oxide in layer/Au/Heat/Mo/Si the Mo layer is thin, so <110> Mo grain boundaries in the semiconductor and oxide layers, the growth direction cannot be detected from FIG. 5a. Both Ni metallic underlayers may consist of metal and oxide material, and Au have ficc crystal structures; however, Au has a larger 55 where grains of metal material have a fec, hop or bcc crystal lattice constant, a, than Ni (a(Ni)=0.3524 nm and a? Au) structure. In an hcp layer, at least 50% of grains have hcp =0.4079 nm). Thus, the size of the lattice constant may be crystal structure. The hcp layer can also consist of at least important in determining the growth direction of Silayer. 50% of grains with hcpcrystal structure surrounded by an Heat may also be an important Sputter parameter for Si oxide grain matrix. In abcc layer, at least 50% of grains have layer growth. If we grow 1) Seed layer/Au/Si, and 2) Seed 60 bcc crystal structure. The bcc layer can also consist of at least layer/Ni/Silayer structures at room temperature, 0-20 scans 50% of grains with bcc crystal structure surrounded with an do not show any Sidiffraction peaks. This indicates that Sihas oxide grain matrix. anamorphous or nanocrystalline structure. Also, the presence The following sets forth four possible compositions of an of heat may be necessary for obtaining epitaxial growth of fcc layer according to various embodiments of the invention: Some semiconductor layers. As described above, the Substrate 65 1) A fecunderlayer may comprise at least one element from may be heated to at least 200° C. (e.g. 300°C.), for example, the group consisting of Al, Ni, Cu, Rh, Pd, Ag, Ir, Pt, Au, prior to Sputtering an Si Semiconductor layer. Heating can be Pb. US 8,981,211 B2 5 6 2) A fecunderlayer may comprise at least one element from Re; at least one element from the group consisting of B. the group consisting of Al, Ni, Cu, Rh, Pd, Ag, Ir, Pt, Au, C, N, O, Na, Si, S. P. K., Al, V, Cr, Mn, Fe, Ni, Cu, Ga, Ge. Pb; and at least one element from the group consisting of Se, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Ta, W, Ir, Pt, B, C, N, O, Na, Si, S. P. K. Sc,Ti,V, Cr, Mn, Fe, Co., Zn, Au, Bi; and at least one oxide material selected from Ga, Ge, Se, Y, Zr, Nb, Mo, Ru, Cd, In, Sn, Sb, Te, Hf, Ta, group consisting of magnesium (Mg) oxide, aluminum W, Re, Bi. (Al) oxide, silicon (Si) oxide, titanium (Ti) oxide, vana 3) A fecunderlayer may comprise at least one element from dium (V) oxide, chromium (Cr) oxide, manganese (Mn) the group consisting of Al, Ni, Cu, Rh, Pd, Ag, Ir, Pt, Au, oxide, iron (Fe) oxide, cobalt (Co) oxide, nickel (Ni) Pb: and at least one oxide material selected from group oxide, copper (Cu) oxide, Zinc (Zn) oxide, (Ga) consisting of: magnesium (Mg) oxide, aluminum (Al) 10 oxide, germanium (Ge) oxide, (Se) oxide, oxide,(V) oxide, silicon chromium (Si) oxide, (Cr) titanium oxide, (Ti) manganese oxide, Vanadium (Mn) yttrium (Y) oxide,ide. zirconiumZi (Z r) oxide,ide, niobium (Nt(Nb) oxide, iron (Fe) oxide, cobalt (Co) oxide, nickel (Ni) oxide, molybdenum (Mo) oxide, (In) oxide, t1n oxide, copper (Cu) oxide, Zinc (Zn) oxide, gallium (Ga) (Sn) oxide, antimony (Sb) oxide, (Tl) oxide, oxide, germanium (Ge) oxide, selenium (Se) oxide, 15 hafnium (Hf) oxide, tantalum (Ta) oxide, tungsten (W) yttrium (Y) oxide, zirconium (Zr) oxide, niobium (Nb) oxide, (Hg) oxide, lead (Pb) oxide, and bismuth oxide, molybdenum (Mo) oxide, indium (In) oxide, (Bi) oxide. (Sn) oxide, antimony (Sb) oxide, tellurium (TI) oxide, The following sets forth four possible compositions of bcc hafnium (Hf) oxide, tantalum (Ta) oxide, tungsten (W) layer: oxide, mercury (Hg) oxide, lead (Pb) oxide, and bismuth 20 1) A bcc underlayer may comprise at least one element (Bi) oxide. from the group consisting of V, Cr, Fe, Nb, Mo, Ta, W. 4) Afcc underlayer may also comprise at least one element 2) A bcc underlayer may comprise at least one element from the group consisting of Al, Ni, Cu, Rh, Pd, Ag, Ir, from the group consisting of V, Cr, Fe, Nb, Mo, Ta, W: Pt, Au, Pb: at least one element from the group consist- and at least one element from the group consisting of B. ing of B, C, N, O, Na, Si, S. P. K. Sc, Ti,V, Cr, Mn, Fe, 25 C, N, O, Na, Si, S. P. K. Sc, Ti, Mn, Co, Ni, Cu, Zn, Ga., Co., Zn, Ga, Ge, Se, Y, Zr, Nb, Mo, Ru, Cd, In, Sn, Sb, Te, Ge, Se, Y, Zr, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Hf, Re, Hf, Ta, W, Re, Bi; and at least one oxide material selected Ir, Pt, Au, Bi. from group consisting of magnesium (Mg) oxide, alu- 3) A bcc underlayer may comprise at least one element minum (Al) oxide, silicon (Si) oxide, titanium (Ti) from the group consisting of V, Cr, Fe, Nb, Mo, Ta, W: oxide, Vanadium (V) oxide, chromium (Cr) oxide, man- 30 and at least one oxide material selected from group ganese (Mn) oxide, iron (Fe) oxide, cobalt (Co) oxide, consisting of magnesium (Mg) oxide, aluminum (Al) nickel (Ni) oxide, copper (Cu) oxide, zinc (Zn) oxide, oxide, silicon (Si) oxide, titanium (Ti) oxide, vanadium gallium (Ga) oxide, germanium (Ge) oxide, selenium (V) oxide, chromium (Cr) oxide, manganese (Mn) (Se) oxide, yttrium (Y) oxide, zirconium (Zr) oxide, oxide, iron (Fe) oxide, cobalt (Co) oxide, nickel (Ni) niobium (Nb) oxide, molybdenum (Mo) oxide, indium 35 oxide, copper (Cu) oxide, Zinc (Zn) oxide, gallium (Ga) (In) oxide, tin (Sn) oxide, antimony (Sb) oxide, tellu- oxide, germanium (Ge) oxide, selenium (Se) oxide, rium (TI) oxide, hafnium (Hf) oxide, tantalum (Ta) yttrium (Y) oxide, zirconium (Zr) oxide, niobium (Nb) oxide, tungsten (W) oxide, mercury (Hg) oxide, lead oxide, molybdenum (Mo) oxide, indium (In) oxide, tin (Pb) oxide, and bismuth (Bi) oxide. (Sn) oxide, antimony (Sb) oxide, tellurium (TI) oxide, The following sets forth four possible compositions of the 40 hafnium (Hf) oxide, tantalum (Ta) oxide, tungsten (W) hcp layer: oxide, mercury (Hg) oxide, lead (Pb) oxide, and bismuth 1) A hep underlayer may comprise at least one element (Bi) oxide. from the group consisting of Sc, Ti, Co., Zn, Y, Zr, Ru, Hf, 4) Abcc underlayer may also comprise at least one element Re. from the group consisting of V, Cr, Fe, Nb, Mo, Ta, W: at 2) A hcp underlayer may comprise at least one element 45 least one element from the group consisting of B, C, N, from the group consisting of Sc, Ti, Co., Zn, Y, Zr, Ru, Hf, O, Na, Si, S. P. K. Sc, Ti, Mn, Co, Ni, Cu, Zn, Ga, Ge, Se, Re; and at least one element from the group consisting of Y, Zr, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Hf, Re, Ir, Pt, B, C, N, O, Na, Si, S. P. K., Al, V, Cr, Mn, Fe, Ni, Cu, Ga., Au, Bi; and at least one oxide material selected from Ge, Se, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Ta, W, Ir, group consisting of magnesium (Mg) oxide, aluminum Pt, Au, Bi. 50 (Al) oxide, silicon (Si) oxide, titanium (Ti) oxide, vana 3) A hcp underlayer may comprise at least one element dium (V) oxide, chromium (Cr) oxide, manganese (Mn) from the group consisting of Sc, Ti, Co., Zn, Y, Zr, Ru, Hf, oxide, iron (Fe) oxide, cobalt (Co) oxide, nickel (Ni) Re; and at least one oxide material selected from group oxide, copper (Cu) oxide, Zinc (Zn) oxide, gallium (Ga) consisting of magnesium (Mg) oxide, aluminum (Al) oxide, germanium (Ge) oxide, selenium (Se) oxide, oxide, silicon (Si) oxide, titanium (Ti) oxide, vanadium 55 yttrium (Y) oxide, zirconium (Zr) oxide, niobium (Nb) (V) oxide, chromium (Cr) oxide, manganese (Mn) oxide, molybdenum (Mo) oxide, indium (In) oxide, tin oxide, iron (Fe) oxide, cobalt (Co) oxide, nickel (Ni) (Sn) oxide, antimony (Sb) oxide, tellurium (TI) oxide, oxide, copper (Cu) oxide, Zinc (Zn) oxide, gallium (Ga) hafnium (Hf) oxide, tantalum (Ta) oxide, tungsten (W) oxide, germanium (Ge) oxide, selenium (Se) oxide, oxide, mercury (Hg) oxide, lead (Pb) oxide, and bismuth yttrium (Y) oxide, zirconium (Zr) oxide, niobium (Nb) 60 (Bi) oxide. oxide, molybdenum (Mo) oxide, indium (In) oxide, tin Seed layer comprises at least one layer with amorphous or (Sn) oxide, antimony (Sb) oxide, tellurium (TI) oxide, nanocrystalline structure. The following sets forth possible hafnium (Hf) oxide, tantalum (Ta) oxide, tungsten (W) compositions of seed layer: oxide, mercury (Hg) oxide, lead (Pb) oxide, and bismuth 1) Seed layer may comprise of silicon nitride SiN. (Bi) oxide. 65 2) Seed layer may comprise at least one element from the 4) Ahcp underlayer may also comprise at least one element group consisting of V, Cr, Mn, Fe, Co, Ni; and at least from the group consisting of Sc, Ti, Co., Zn, Y, Zr, Ru, Hf, one element from the group consisting of B, C, Al. Si, P. US 8,981,211 B2 7 8 Sc, Ti, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sulfide (CuS (X varies from 1 to 2)), copper (Cu In, Sn, Te, Hf, Ta, W, Re, Ir, Pt, Au. Se(x varies from 1 to 2)), copper indium disulfide (CuInS), 3) Seed layer may be composed of 10 to 96 at. '% of least copper gallium disulfide (CuGaS), copper indium gallium one element from the group consisting of V, Cr, Mn, Fe, disulfide, (Cu(In Ga)S (X varies from 0 to 1)), copper Co, Ni; and 4 to 50 at. 9% of least one element from the indium diselenide (CuInSe2), copper gallium diselenide (Cu group consisting of B, C, P. Si, Ti, Ge, Zr, Mo, Hf, Ta, W. GaSea), copper indium gallium diselenide (Cu(In Ga)Se2 4) Seed layer may be composed of 10 to 90 at. '% of least (x varies from 0 to 1)), copper silver indium gallium disulfide one element from the group consisting of V, Cr, Mn, Fe, (Cu, Ag, )(In Ga)S (x varies from 0 to 1, y varies from 0 Co, Ni; 4 to 50 at.% of least one element from the group to 1)), copper silver indium gallium diselenide (Cu, Ag) consisting of B, C, P. Si, Ti, Ge, Zr, Mo, Hf, Ta, W.; and 10 (Ini-Ga,)Se: (X varies from 0 to 1, y varies from 0 to 1)), at least one element from the group consisting of Al, Sc., (CuAu)lnS (X varies from 0 to 1), (Cu, Au)CuGaS (X Cu, Zn, Ga, Sr, Y. Ru, Rh, Pd, Ag, In, Sn, Te, Re, Ir, Pt, varies from 0 to 1), (Cu, Au, )(In-Ga,)S(X varies from 0 to Au. 1, y varies from 0 to 1), (CuAu)InSea (x varies from 0 to 1), Structures with Epitaxially-Grown Semiconductor (Cu, Au)GaSe (X varies from 0 to 1), (Cu, Au)(In Ga) Layers 15 Se (X varies from 0 to 1), (Ag-Au)(In Ga)Se (X varies The structures discussed above for promoting epitaxial from 0 to 1), (Cu, Ag, Au, )(In-Ga.)Sea (x varies from 0 to growth of semiconductor layers may be used in Solar cells as 1, y Varies from 0 to 1, Z varies from 0 to 1), (Cu, Au)S (X illustrated in FIGS. 15, 16a and 16b. Solar cells with epitaxi varies from 0 to 1), (Ag-Au)S (X varies from 0 to 1), ally grown semiconductor layers may comprise one of the (Cu, Ag, Au),S(X varies from 0 to 1, y varies from 0 to 1), following example layer structures: indium sulfide (InS), indium selenide (InSes), aluminum 1) Underlayer1/semiconductor layers/top conductive and nitride (AIN), indium nitride (InN), gallium nitride (GaN), transparent layers; bismuth sulfide (BiS), antimony sulfide (SbS), silver sul 2) Underlayer1/Underlayer2/semiconductor layers/top fide (AgS), tungsten sulfide (WS), tungsten selenide conductive layers; (WSea), molybdenum sulfide (MoS), molybdenum selenide 3) Underlayer1/Underlayer2/Underlayer3/semiconductor 25 (MoSea), tin sulfide (SnS (x varies from 1 to 2)), tin selenide layers/top conductive and transparent layers; (SnSe (x varies from 1 to 2)), coppertin sulfide (CuSnS). 4) Underlayer1/Underlayer2/Underlayer3/Underlayer4/ The semiconductor layers may also contain up to 80 vol.% semiconductor layers/top conductive and transparent of an oxide material selected from the group consisting of layers; magnesium (Mg) oxide, aluminum (Al) oxide, silicon (Si) 5) Seed layer/Underlayer1/semiconductor layers/top con 30 oxide, titanium (Ti) oxide, Vanadium (V) oxide, chromium ductive and transparent layers; (Cr) oxide, manganese (Mn) oxide, iron (Fe) oxide, cobalt 6) Seed layer/Underlayer1/Underlayer2/semiconductor (Co) oxide, nickel (Ni) oxide, copper (Cu) oxide, zinc (Zn) layers/top conductive and transparent layers; oxide, gallium (Ga) oxide, germanium (Ge) oxide, selenium 7) Seed layer/Underlayer1/Underlayer2/Underlayer3/ (Se) oxide, yttrium (Y) oxide, zirconium (Zr) oxide, niobium semiconductor layers/top conductive and transparent 35 (Nb) oxide, molybdenum (Mo) oxide, indium (In) oxide, tin layers; and (Sn) oxide, antimony (Sb) oxide, tellurium (TI) oxide, 8) Seed layer/Underlayer1/Underlayer2/Underlayer3/Un hafnium (Hf) oxide, tantalum (Ta) oxide, tungsten (W) oxide, derlayer4/semiconductor layers/top conductive and mercury (Hg) oxide, lead (Pb) oxide, and bismuth (Bi) oxide. transparent layers. An n-type semiconductor layer may include at least one Up to 100 underlayers can be used to promote desired crys 40 n-type semiconductor material selected from the group con tallographic orientation of semiconductor layer as shown in sisting of silicon (Si), germanium (Ge), tin (Sn), beta iron FIG. 14. silicide (B-FeSi), indium antimony (InSb), indium arsenic The semiconductor layers in the Solar cells may include at (InAs), indium phosphate (InP), gallium phosphate (GaP), least one p-type semiconductor layer, and at least one n-type aluminum phosphate (AlP), gallium arsenic (GaAs), gallium semiconductor layer (see example FIG. 15). One or more of 45 antimony (GaSb), aluminum antimony (AlSb), silicon car the semiconductor layers can be composed of an intrinsic bide (SiC), tellurium (Te), zinc antimony (ZnSb), mercury semiconductor material. FIG. 15 shows an n-type semicon (HgTe), led sulfide (PbS), led selenide (PbSe), led ductor layer disposed over a p-type semiconductor layer. In telluride (PbTe), cadmium sulfide (CdS), cadmium selenium other implementations, p-type semiconductor layers may be (CdSe), cadmium tellurium (CdTe), zinc sulfide (ZnS), Zinc disposed over n-type semiconductor layers. In addition, U.S. 50 selenide (ZnSe), (ZnTe), (SnTe), application Ser. Nos. 12/016,172, 11/923,036, and 11/923, copper Sulfide (CuS (X varies from 1 to 2)), 070 all of which are incorporated by reference herein in their (CuSe (X varies from 1 to 2)), copper indium disulfide entirety for all purposes, disclose additional layer arrange (CuInS), copper gallium disulfide (CuGaS), copper indium ments and configurations for photovoltaic cell structures that gallium disulfide. (Cu(In Ga)S (X varies from 0 to 1)), can be incorporated into embodiments of the invention. 55 copper indium diselenide (CuInSe2), copper gallium dis The semiconductor layers may include at least one semi elenide (CuCaSea), copper indium gallium diselenide (Cu conductor material selected from the group consisting of (In Ga)Se (X varies from 0 to 1)), copper silver indium silicon (Si), germanium (Ge), tin (Sn), beta iron silicide gallium disulfide-(Cu, Ag, )(In Ga)S (x varies from 0 to (B-FeSi), indium antimony (InSb), indium arsenic (InAs), 1, y varies from 0 to 1)), copper silver indium gallium dis indium phosphate (InP), gallium phosphate (GaP), aluminum 60 elenide (Cu, Ag,)(Ini-Ga,)Sea (x varies from 0 to 1, y Var phosphate (AlP), gallium arsenic (GaAs), gallium antimony ies from 0 to 1)), (Cu, Au)InS (x varies from 0 to 1), (GaSb), aluminum antimony (AlSb), silicon carbide (SiC), (CuAu)CuGaS (X varies from 0 to 1), (CuAu)(In tellurium (Te). Zinc antimony (ZnSb), mercury telluride Ga)S(X varies from 0 to 1, y varies from 0 to 1), (Cu, Au,) (HgTe), led sulfide (PbS), led selenide (PbSe), led telluride In Se (X varies from 0 to 1), (Cu, Au)GaSe (X varies from (PbTe), cadmium sulfide (CdS), cadmium selenium (CdSe), 65 0 to 1), (Cu, Au)(In Ga)Se (X varies from 0 to 1), (Age cadmium tellurium (CdTe), zinc sulfide (ZnS), Au, )(In-Ga.)Se: (X varies from 0 to 1), (Cu, Ag, Au,) (ZnSe), zinc telluride (ZnTe), tin telluride (SnTe), copper (In Ga)Sea (x varies from 0 to 1, y varies from 0 to 1, Z US 8,981,211 B2 9 10 varies from 0 to 1), (Cu, Au)S (x varies from 0 to 1), elements such as (B), gallium (Ga), indium (In), or (Ag-Au,)S (x varies from 0 to 1), (Cu, Ag, Au,),S (X aluminum (Al), in order to increase the number of free (in this varies from 0 to 1, y varies from 0 to 1), indium sulfide case positive (hole)) charge carriers. (InS), indium selenide (InSes), aluminum nitride (AIN), One or more of the p-type semiconductor layers may also indium nitride (InN), gallium nitride (GaN), bismuth sulfide contain up to 80 vol.% of oxide material selected from the (BiS), antimony Sulfide (Sb2S), silver Sulfide (AgS), group consisting magnesium (Mg) oxide, aluminum (Al) tungsten sulfide (WS), tungsten selenide (WSea), molybde oxide, silicon (Si) oxide, titanium (Ti) oxide, vanadium (V) num sulfide (MoS), molybdenum selenide (MoSea), tinsul oxide, chromium (Cr) oxide, manganese (Mn) oxide, iron fide (SnS, (x varies from 1 to 2)), tin selenide (SnSe(x varies (Fe) oxide, cobalt (Co) oxide, nickel (Ni) oxide, copper (Cu) from 1 to 2)), copper tin Sulfide (CuSnS). Such semicon 10 ductors may be doped by adding an impurity of Valence-five oxide, Zinc (Zn) oxide, gallium (Ga) oxide, germanium (Ge) elements such as nitrogen (N), phosphorus (P), arsenic (AS), oxide, selenium (Se) oxide, yttrium (Y) oxide, zirconium (Zr) or antimony (Sb)), in order to increase the number of free (in oxide, niobium (Nb) oxide, molybdenum (Mo) oxide, indium this case negative (electron)) charge carriers. (In) oxide, tin(Sn) oxide, antimony (Sb) oxide, tellurium (Tl) One or more of the n-type semiconductor layers may also 15 oxide, hafnium (Hf) oxide, tantalum (Ta) oxide, tungsten (W) contain up to 80 vol.% of oxide material selected from the oxide, mercury (Hg) oxide, lead (Pb) oxide, and bismuth (Bi) group consisting magnesium (Mg) oxide, aluminum (Al) oxide. oxide, silicon (Si) oxide, titanium (Ti) oxide, vanadium (V) U.S. application Ser. Nos. 12/016,172, 11/923,036, and oxide, chromium (Cr) oxide, manganese (Mn) oxide, iron 11/923,070 all of which are incorporated by reference herein (Fe) oxide, cobalt (Co) oxide, nickel (Ni) oxide, copper (Cu) in their entirety for all purposes, disclose photovoltaic struc oxide, Zinc (Zn) oxide, gallium (Ga) oxide, germanium (Ge) tures having a photoactive conversion layer comprising one oxide, selenium (Se) oxide, yttrium (Y) oxide, zirconium (Zr) or more granular semiconductor and oxide layers with oxide, niobium (Nb) oxide, molybdenum (Mo) oxide, indium nanometer-size semiconductor grains Surrounded by a matrix (In) oxide, tin(Sn) oxide, antimony (Sb) oxide, tellurium (Tl) of oxide. oxide, hafnium (Hf) oxide, tantalum (Ta) oxide, tungsten (W) 25 The top conductive layers may consist of at least one con oxide, mercury (Hg) oxide, lead (Pb) oxide, and bismuth (Bi) ductive layer. This layer may also be transparent to the Solar oxide. radiation. This will allow photons to reach semiconductor The p-type semiconductor layers may comprise at least one layers for conversion into electrical energy. The conductive p-type semiconductor material selected from the group con layer may comprise an oxide material selected from the group sisting of silicon (Si), germanium (Ge), tin (Sn), beta iron 30 consisting magnesium (Mg) oxide, aluminum (Al) oxide, silicide (B-FeSi), indium antimony (InSb), indium arsenic silicon (Si) oxide, titanium (Ti) oxide, vanadium (V) oxide, (InAs), indium phosphate (InP), gallium phosphate (Gap), chromium (Cr) oxide, manganese (Mn) oxide, iron (Fe) aluminum phosphate (AlP), gallium arsenic (GaAs), gallium oxide, cobalt (Co) oxide, nickel (Ni) oxide, copper (Cu) antimony (GaSb), aluminum antimony (AlSb), silicon car oxide, Zinc (Zn) oxide, gallium (Ga) oxide, germanium (Ge) bide (SiC), tellurium (Te), zinc antimony (ZnSb), mercury 35 oxide, selenium (Se) oxide, yttrium (Y) oxide, zirconium (Zr) telluride (HgTe), led sulfide (PbS), led selenide (PbSe), led oxide, niobium (Nb) oxide, molybdenum (Mo) oxide, indium telluride (PbTe), cadmium sulfide (CdS), cadmium selenium (In) oxide, tin(Sn) oxide, antimony (Sb) oxide, tellurium (Tl) (CdSe), cadmium tellurium (CdTe), zinc sulfide (ZnS), Zinc oxide, hafnium (Hf) oxide, tantalum (Ta) oxide, tungsten (W) selenide (ZnSe), Zinc telluride (ZnTe), tin telluride (SnTe). oxide, mercury (Hg) oxide, lead (Pb) oxide, and bismuth (Bi) copper sulfide (CuS (X varies from 1 to 2)), copper selenide 40 oxide. For example the top conductive layers structure may (CuSe (X varies from 1 to 2)), copper indium disulfide consist of ZnO layer that is formed over the semiconductor (CuInS), copper gallium disulfide (CuGaS), copper indium layer and a combination of Zinc and aluminum oxide (ZnO-- gallium disulfide, (Cu(In Ga)S (X varies from 0 to 1)), Al-O.) layer that is formed over the ZnO layer. In another copper indium diselenide (CuInSe2), copper gallium dis example a TiO, layer is formed over the semiconductor layer elenide (CuCaSea), copper indium gallium diselenide (Cu 45 and indium thin oxide (ITO) is formed over the TiO, layer. (In Ga)Se (X varies from 0 to 1)), copper silver indium FIGS. 16a and 16b illustrate example structures and con gallium disulfide (Cu, Ag, )(In Ga.)S (x varies from 0 to figurations of Solar cells, according to possible implementa 1, y varies from 0 to 1)), copper silver indium gallium dis tions of the invention, that incorporate the layer structures elenide (Cu, Ag,)(In-Ga.)Se: (X varies from 0 to 1, y var discussed above. As FIG. 16a illustrates, Solar cell 101 a may ies from 0 to 1)), (Cu, Au)InS (x varies from 0 to 1), 50 comprise (in overlying sequence) transparent substrate 8000 (Cu, Au,)CuGaS (X varies from 0 to 1), (Cu, Au, )(In or non-transparent substrate 8600, contact layer 9000, pho Ga)S (x varies from 0 to 1, y varies from 0 to 1), (Cu, Au,) toactive conversion layer 80, transparent conductive layer InSe (X varies from 0 to 1), (Cu, Au)GaSe (X varies from 7000, and transparent material layer 8000. In some imple 0 to 1), (Cu, Au)(In Ga)Se (X varies from 0 to 1), (Ag mentations, the transparent layer 8000 may be glass, plastic Au, )(In-Ga,)Se: (X varies from 0 to 1), (Cu, Ag, Au,) 55 or other Suitable protective material. In some implementa (In Ga)Sea (x varies from 0 to 1, y varies from 0 to 1, Z tions, the transparent layer 8000 may be glass, plastic or other varies from 0 to 1), (Cu, Au)S (x varies from 0 to 1), suitable protective material. Contact layer 9000 may com (Ag-Au,)2S (x varies from 0 to 1), (Cu, Ag, Au,)2S (X prise set of Seed layers and Underlayers as described above. varies from 0 to 1, y varies from 0 to 1), indium sulfide As FIG. 16b illustrates, photoactive conversion layer 80 may (InS), indium selenide (InSes), aluminum nitride (AIN), 60 include a plurality of Sub-layers including one or more of a indium nitride (InN), gallium nitride (GaN), bismuth sulfide seed layer 6000, one or more interlayers 5000 (in this imple (BiS), antimony Sulfide (Sb2S), silver Sulfide (AgS), mentation, the seed layer 6000 and underlayers 5000 may tungsten sulfide (WS), tungsten selenide (WSea), molybde replace the contact layer 9000), one or more n-type semicon num sulfide (MoS), molybdenum selenide (MoSea), tinsul ductor and oxide layers 2101, and a hole conducting material fide (SnS (x varies from 1 to 2)), tin selenide (SnSe (X varies 65 layer 3000. As the foregoing description demonstrates, the from 1 to 2)), copper tin Sulfide (CuSnS). Such semicon structure and configuration of the conversion layer 80 may ductors may be doped by adding an impurity of valence-three vary considerably. US 8,981,211 B2 11 12 Transparent layer 8000 can be a glass substrate or depos underlayer should be lower than the work function of the ited layer made of a variety of materials, such as silicon overlaying semiconductor to achieve Ohmic contact. dioxide. Alternatively, a transparent polymer can be used. The workfunction of some p-type semiconductors is larger Still further, one or more of the transparent conducting layers than that of metal materials. In this case, an Ohmic contact 7000 can be replaced by conductive oxide layer and metal can be achieved by depositing a thin highly doped p-type contacts arranged in a grid (e.g., fingers and busbars). Addi semiconductor before depositing the p-type semiconductor tional layers, such as anti-reflection coatings can also be layer with the large work function. This creates a thin highly added. The layer stack can be deposited on glass, polymer or doped region that carriers can tunnel through. Another way to metal Substrates. If the layer stack is deposited on top of a achieve an Ohmic contact is to deposit a very low band 10 semiconductor material, such as Sb2Te3, or an oxide before non-transparent Substrate, the top contact is transparent to depositing the p-type semiconductor layer with the large allow light penetration into the photoactive conversion layer. work function. Transparent substrate layer 8000 can be replaced by other In the previous description, numerous specific details are Suitable protective layers or coatings, or be added during set forth, such as specific materials, structures, processes, construction of a solar module or panel. Still further, the 15 etc., in order to provide a better understanding of the present layers described herein may be deposited on a flat substrate invention. However, the present invention can be practiced (such as a glass Substrate intended for window installations), without resorting to the details specifically set forth. In other or directly on one or more Surfaces of a non-imaging Solar instances, well-known processing materials and techniques concentrator, such as a trough-like or Winston optical con have not been described in detail in order not to unnecessarily CentratOr. obscure the present invention. Only the preferred embodi The following sets forth an example manufacturing pro ments of the present invention and but a few examples of its cess for fabrication of solar cells that combines physical and versatility are shown and described in the present disclosure. chemical vapor depositions. First, a physical vapor deposition It is to be understood that the present invention is capable of (PVD) is used to deposit one of the following layer structures: use in various other combinations and is susceptible of 1) Underlayer1/semiconductor layers (FIG. 6); 25 changes and/or modifications within the scope of the inven 2) Underlayer1/Underlayer2/semiconductor layers (FIG. tive concept as expressed herein. 7); What is claimed is: 3) Underlayer1/Underlayer2/Underlayer3/semiconductor 1. A photovoltaic cell, comprising layers (FIG. 8): a non-textured substrate; 4) Underlayer1/Underlayer2/Underlayer3/Underlayer4/ 30 a non-magnetic amorphous or nanocrystalline seed layer semiconductor layers (FIG. 9); disposed over the substrate, the 5) Seed layer/Underlayer1/semiconductor layers (FIG. seed layer being a metallic material; 10); an underlayer comprising one or more metallic Sub-layers 6) Seed layer/Underlayer1/Underlayer2/semiconductor deposited over the seed layer, layers (FIG. 11): 35 wherein the underlayer layer promotes growth in a first 7) Seed layer/Underlayer1/Underlayer2/Underlayer3/ growth direction of a majority of grains of one or more semiconductor layers (FIG. 12); or overlying semiconductor layers; 8) Seed layer/Underlayer1/Underlayer2/Underlayer3/Un a first semiconductor layer comprising an electron con derlayer4/semiconductor layers (FIG. 13). ducting material; The foregoing layer structures, in one implementation, are 40 a second semiconductor layer comprising a hole conduct deposited on top of non-single crystal Substrates. As dis ing material; and cussed above, seed layer and underlayers are used to achieve a transparent conductive layer. epitaxial growth of the semiconductor layers using PVD. 2. The photovoltaic cell of claim 1 wherein the first semi Then, a chemical vapor deposition (CVD) is used to deposit conductor layer comprises two or more semiconductor Sub additional semiconductor layers on top of PVD-deposited 45 layers each comprising a hole conducting material. epitaxial semiconductor layers. Semiconductors deposited 3. The photovoltaic cell of claim 1 wherein the second using CVD have low defect concentration. This is one of the semiconductor layer comprises two or more semiconductor main reasons for growing Si-based solar cells using CVD. Sub-layers each comprising an electron conducting material. Furthermore, high deposition rates can be reached using 4. The photovoltaic cell of claim 1 wherein the first semi CVD. The semiconductor layers are covered with a top con 50 conductor layer comprises two or more semiconductor Sub tact that can be deposited by either PVD or CVD. The top layers each comprising a hole conducting material and the contact should be conductive and, in most of cases, transpar second semiconductor layer comprises two or more semicon ent. In these solar cell structures, semiconductor layers are ductor Sub-layers each comprising an electron conducting used to convert light into charge carriers. To achieve charge material. separation and produce photovoltaic effect, semiconductor 55 5. A photovoltaic cell, comprising layers are comprised of at least one p-type and at least one a non-textured substrate; n-type semiconductor. The main advantage of this process is a non-magnetic amorphous or nanocrystalline seed layer growth of epitaxial semiconductor layers on top of non-single disposed over the Substrate, the seed layer being a metal crystal Substrates, such as metal, plastic or glass Substrate. lic material; To increase the efficiency of solar cells, it may be desirable 60 an fec underlayer with <111 >growth directions formed to form an Ohmic contact between the metallic underlayer over the seed layer; and the overlaying semiconductor layer. If the overlaying abcc underlayer with <110>growth directions formed over semiconductor layer is a p-type semiconductor, the work the fecunderlayer, wherein the bcc underlayer promotes function of metal underlayer should be larger than the work growth in a first growth direction of a majority of grains function of the overlaying semiconductor to achieve Ohmic 65 of one or more overlying semiconductor layers; contact. On the other hand, if the overlaying semiconductor a first semiconductor layer comprising an electron con layer is n-type semiconductor, the work function of the metal ducting material; US 8,981,211 B2 13 14 a second semiconductor layer comprising a hole conduct 10 to 90 at.% of least one element from the group consist ing material; and ing of V. Cr, Mn, Fe, Co, and Ni; a transparent conductive layer. 4 to 50 at.% of least one element from the group consisting 6. The photovoltaic cell of claim 5 wherein the first semi of B, C, P. Si, Ge, Zr, Mo, Hf, Ta, and W. and conductor layer is formed over the second semiconductor at least one element from the group consisting of Al, Sc., Ti, layer, and wherein the second semiconductor layer is formed Cu, Zn, Ga, Sr, Y. Ru, Rh, Pd, Ag, In, Te, Sn, Re, Ir, Pt, over the bcc underlayer. and Au. 7. The photovoltaic cell of claim 5 wherein the second 20. The photovoltaic cell of claim 16 wherein at least one semiconductor layer is formed over the first semiconductor seed layer comprises at least one element selected from the layer. 10 8. The photovoltaic cell of claim 5 wherein at least one of group consisting of B. P. Sc, Ti, V. Cr, Mn, Fe, Co, Ni, Cu, Y. the first and second semiconductor layers comprises one or Zr, Nb, Mo, Ru, Rh, Pd, Ag, In, Te, Hf, Ta, W, Re, Ir, Pt, and more semiconductor and oxide layers comprising an oxide Au. and a semiconductor, wherein the oxide is dispersed at grain 21. The photovoltaic cell of claim 1 wherein the underlayer boundaries of the semiconductor. 15 comprises at least one metallic material having ahcp or fcc or 9. The photovoltaic cell of claim 1 wherein the first semi bcc lattice structure. conductor layer or the second semiconductor layer is depos 22. The photovoltaic cell of claim 21 wherein the metallic ited onto the underlayer layer. material of the underlayer has the hcp lattice structure and 10. The photovoltaic cell of claim 1 wherein the underlayer wherein the underlayer comprises at least one element from comprises at least one metallic material having hcp or fcc or the group consisting of Sc, Ti, Co., Zn, Y, Zr, Ru, Hf, and Re. bcc lattice structure with a <0001 dor <111>or <110>growth 23. The photovoltaic cell of claim 21 wherein the metallic directions. material of the underlayer has the hcp lattice structure and 11. The photovoltaic cell of claim 1 wherein the underlayer wherein the underlayer comprises: comprises at least two metallic materials, wherein a first at least one element from the group consisting of Sc., Ti, Co. metallic material of the underlayer has anhcp lattice structure 25 Zn, Y, Zr, Ru, Hf, and Re; and with <0001 >growth directions and a second metallic material at least one element from the group consisting of B, C, N, of the underlayer has an fec lattice structure with 0, Na, Si, S. P. K., Al, V, Cr, Mn, Fe, Ni, Cu, Ga, Ge, Se, <111>growth directions. Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Ta, W, Ir, Pt, Au, 12. The photovoltaic cell of claim 1 wherein the underlayer and Bi. comprises at least two metallic materials, wherein a first 30 24. The photovoltaic cell of claim 21 wherein the metallic metallic material of the underlayer has an fec lattice structure material of the underlayer has the fec lattice structure and with <111 >growth directions and a second metallic material wherein the underlayer comprises at least one element from of the underlayer has abcc lattice structure with <110>growth the group consisting of Al, Ni, Cu, Rh, Pd, Ag, Ir, Pt, Au, and directions. Pb. 13. The photovoltaic cell of claim 1 wherein the underlayer 35 25. The photovoltaic cell of claim 21 wherein the metallic comprises at least two metallic materials, wherein a first material of the underlayer has the fec lattice structure and metallic material of the underlayer has anhcp lattice structure wherein the underlayer comprises: with <0001 >growth directions and a second metallic material at least one element from the group consisting of Al, Ni, of the underlayer has abcc lattice structure with <110>growth Cu, Rh, Pd, Ag, Ir, Pt, Au, and Pb: and directions. 40 at least one element from the group consisting of B, C, N, 14. The photovoltaic cell of claim 1 wherein the underlayer 0, Na, Si, S. P. K. Sc, Ti,V, Cr, Mn, Fe, Co., Zn, Ga, Ge. comprises at least three metallic materials, wherein a first Se, Y, Zr, Nb, Mo, Ru, Cd, In, Sn, Sb, Te, Hf, Ta, W, Re, metallic material of the underlayer has a ficc lattice structure and Bi. with <111 >growth directions, a second metallic material of 26. The photovoltaic cell of claim 21 wherein the metallic the underlayer has a hep lattice structure with <0001 >growth 45 material of the underlayer has the bcc lattice structure and directions, and a third metallic material of the underlayer has wherein the underlayer comprises at least one element from abcc lattice structure with <110>growth directions. the group consisting of V, Cr, Fe, Nb, Mo, Ta, W. 15. The photovoltaic cell of claim 1 wherein the seed layer 27. The photovoltaic cell of claim 21 wherein the metallic comprises SiN. material of the underlayer has the bcc lattice structure and 16. The photovoltaic cell of claim 1 wherein the seed layer 50 wherein the underlayer comprises: comprises at least one metallic nanocrystalline or amorphous at least one element from the group consisting of V, Cr, Fe, layer. Nb, Mo, Ta, and W. and 17. The photovoltaic cell of claim 16 wherein at least one at least one element from the group consisting of B, C, N, seed layer comprises: 0, Na, Si, S. P. K. Sc, Ti, Mn, Co, Ni, Cu, Zn, Ga, Ge, Se, at least one element from the group consisting of V, Cr, Mn, 55 Y, Zr, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Hf, Re, Ir, Pt, Fe, Co, and Ni; and Au, and Bi. at least one element from the group consisting of B, C, Al. 28. The photovoltaic cell of claim 1 wherein the underlayer Si, P. Sc, Ti, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ru, Rh, comprises at least one metallic material having an hcp lattice Pd, Ag, In, Sn, Te, Hf, Ta, W. Re, Ir, Pt, and Au. structure with <0001 >growth directions or an fec lattice 18. The photovoltaic cell of claim 16 wherein at least one 60 structure with <111>growth directions, or a bcc lattice struc seed layer comprises: ture with <110>growth directions. 10 to 96 at.% of least one element from the group consist 29. The photovoltaic cell of claim 1 wherein the underlayer ing of V. Cr, Mn, Fe, Co, and Ni; and comprises at least two metallic materials, wherein a first 4 to 50 at.% of least one element from the group consisting metallic material of the underlayer has a hep lattice structure of B, C, P. Si, Ti, Ge, Zr, Mo, Hf, Ta, and W. 65 with <0001 >growth directions and a second metallic material 19. The photovoltaic cell of claim 16 wherein at least one of the underlayer has a ficclattice structure with <111 >growth seed layer comprises: directions. US 8,981,211 B2 15 16 30. The photovoltaic cell of claim 1 wherein the underlayer comprises at least two metallic materials, wherein a first metallic material of the underlayer has a ficc lattice structure with <111 >growth directions and a second metallic material of the at least two metallic materials has abcc lattice structure with <110>growth directions. 31. The photovoltaic cell of claim 1 wherein the underlayer comprises at least two metallic materials, wherein a first metallic material of the underlayer has a hep lattice structure with <0001 >growth directions and a second metallic material 10 of the at least two metallic materials has abcc lattice structure with <110>growth directions. 32. The photovoltaic cell of claim 1, wherein the under layer promotes Substantially epitaxial growth of one or more overlying semiconductor layers. 15 33. The photovoltaic cell of claim 1, wherein the under layer promotes textured growth of one or more overlying semiconductor layers. 34. The photovoltaic cell of claim 1, wherein the seed layer promotes growth in a second growth direction of a majority of 20 grains of the overlying underlayer.

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