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United States Patent [19] [111 4,116,733 Olsen Et Al

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United States Patent [19] [111 4,116,733 Olsen Et Al United States Patent [19] [111 4,116,733 Olsen et al. [45] Sep. 26, 1978 [54] VAPOR PHASE GROWTH TECHNIQUE OF Phosphine” J. Electrochem. SOC.,vol. 113, No. 7, Jul. 111-V COMPOUNDS UTILIZING A 1966, pp. 724-728. PREHEATING STEP Gabor, T., “Epitaxial Growth of Gallium Arsenide on Germanium Substrates” IBID., vol. 111, No. 7, Jul. [75] Inventors: Gregory Hammond Olsen, Dayton, 1964, pp. 817-820. N.J.; Thomas Joseph Zamerowski, Barber, G. F., “Two-Chamber Air-to-Vacuum Lock Yardley; Charles Joseph Buiocchi, System” I.B.M. Tech. Discl. Bull., vol. 11, No. 7, Dec. Levittown, both of Pa. 1968, pp. 757-758. [73] Assignee: RCA Corporation, New York, N.Y. Grochowski et al., “Slow Cooling to Minimize Distor- tion -” IBID., vol. 14, No. 5, Oct. 1971, p. 1640. [21] Appl. No.: 840,039 Primary Examiner-L. Dewayne Rutledge [22] Filed: Oct. 6,1977 Assistant Examiner-W. G. Saba Atforney, Agent, or Firm-H. Christoffersen; B. E. [51] Int. Cl.2 ........................................... HOlL 21/205 HO 1L/29/30; H01L/29/38 Moms [52] U.S. Cl. ..................................... 148/175; 148A.5; [571 ABSTRACT 148/174; 156/6 1%.156/613; 1561614 In the vapor phase epitaxy fabrication of semiconductor [58] Field of Search ........................ 148/174, 175, 1.5; 156/612, 613, 614; 427/87,226; 118/49.5 devices and in particular semiconductor lasers, the de- position body on which a particular layer of the laser is [561 References Cited to be grown is preheated to a temperature about 40” to U.S.PATENT DOCUMENTS 60” C. lower than the temperature at which deposition occurs. It has been discovered that by preheating at this 3,314,393 4/1967 Haneta ............................. 148/175 X lower temperature there is reduced thermal decomposi- 3,441,453 4/1969 Conrad et al. ....................... 148/175 tion at the deposition surface, especially for semicon- 3,473,510 10/1969 Sheng et al. ........................ 118/49.5 ductor materials such as indium gallium phosphide and 3,480,491 11/1969 Reisman et al. ................. 148/175 X 3,615,931 10/1971 Arthur ................................. 148/175 gallium arsenide phosphide. A reduction in thermal 3,672,948 6/1972 Foehring et al. ................... 118/49.5 decomposition reduces imperfections in the deposition 3,893,876 7/1975 Akai et al. ............................ 148/175 body in the vicinity of the deposition surface, thereby 3,984,263 10/1976 Asao et al. ....................... 156/614 X providing a device with higher efficiency and longer lifetime. OTHER PUBLICATIONS Tietjen et al., “Preparation - GaArP using Arsine and 5 Claims, 4 Drawing Figures /I0 20 14 12 16 18 GAS /30 GAS GAS GAS GAS INLET 6AS INLET OUTLET INLET OUTLET 52 42 44 46 40 I Go SOURCE SUBSTRATE HOLDER J==TGAS INLET PREHEAT DEPOSITION MIXING SOURCE U 54 ZONE 34 I ZONE 36 THE40I ZONE38 1 In‘ GAS ‘SUBSTRATE SOURCE INLET ENTRY VALVE 50 57 56 U.S. Patent Sept. 26, 1978 Sheet 1 of 2 4,116,733 -0 U.S. Patent Sept. 26, 1978 Sheet 2 of 2 4,116,733 DISLOCATION LOOPS Fig.3. Fig. 4. I * 1 4,116,733 L FIG. 3 is a cross-sectional electron micrograph of the VAPOR PHASE GROWTH TECHNIQUE OF 111-V interfacial region between a gallium arsenide phosphide COMPOUNDS UTILIZING A PREHEATING STEP layer and an indium gallium phosphide layer made by prior art techniques. The Government has rights in this invention pursuant 5 FIG. 4 is a cross-sectional electron micrograph of the to Contract No. NAS1-14349 awarded by NASA, the interfacial region between a gallium arsenide phosphide National Aeronautics and Space Administration. layer and an indium gallium phosphide layer made ac- The present invention relates to vapor phase growth cording to the method of the present invention. techniques and in particular to improved vapor phase DETAILED DESCRIPTION OF THE growth techniques for 111-V compound semiconductor 10 INVENTION devices. ' Referring to FIG. 1, a gallium arsenide phosphide BACKGROUND OF THE INVENTION and indium gallium phosphide semiconductor laser is It is well understood by those skilled in the semicon- set forth herein for the purpose of describing the ductor art that a 111-V semiconductor compound is one l5 method of the present invention, although the method which includes elements from group I11 and V of the of the present invention can be utilized in the fabrication Periodic Table of Elements. of many other 111-V semiconductor devices as well. Many 111-V heterojunction devices, such as transmis- The semiconductor laser is herein designated as 10. sion photocathodes and lasers, depend greatly on high The semiconductor laser 10 includes an active layer quality, defect-free interfaces for good performance. 2o 12 of GaAsl,Px where x is beteen about 0.1 and 0.4. Even after defect-free interfaces have been obtained, Contiguous to the active layer 12 and spaced opposite thermal decomposition can still severely limit device each other are fvst and second confining layers 14 and properties. It has been discovered that many 111-V 16, each of In,,Ga$, where y is between about 0.25 and heretojunction devices, and in particular lasers grown 0.5. Typically, the active layer 12 is undoped and the 25 first confining layer 14 is of P type conductivity and the by vapor phase epitaxial techniques, have suffered from second confining layer 16 is of N type conductivity. thermal decomposition at the interfacial regions. The The second confining layer 16 is on a surface of a sub- thermal decomposition results in defects in the deposi- strate 18 opposite the active layer 12. The substrate 18 is tion body in the area of the deposition surface which of a material capable of forming an ohmic contact with causes reduced device eficiencv and reduced device In 5u the second confining layer 16, e.g., G~As.,P.~,and is of lifetime. the same conductivity type as the second confining The vapor phase growth of many multi-layered 111-V layer 16. On a surface of the first confining layer 14 is an hetetojunction devices typically include the preheating electrode 20 of a material capable of forming an ohmic of the depositing body and deposition surface at the contact to the first confining layer 14. The electrode 20 temperature used for deposition of the growth layer. 35 is of the same conductivity type as the fust confining Typically, for material such as indium gallium arsenide layer 14 and for purposes of the present invention it is of and gallium arsenide phosphide, this temperature is G~AS,,.~~P,,.~~Typically, the active layer 12 is about 0.2 about 700". It is believed that those skilled in the art did micrometer in thickness and each of the first and second not realize that preheating of 111-V materials like indium confining layers 14 and 16 are about 1 micrometer in gallium phosphide or gallium arsenide phosphide to a 40 thickness: the substrate 18 is about 250-300 micrometers temperature of 700" C. would cause thermal decomposi- in thickness; and the electrode 20 is about 1 micrometer tion. Applicants have found from studying transmission in thickness. The conductivity concentration of the first electron micrographs that there is thermal decomposi- confining layer 14 is assumed to be about 5 x 10*8/cm3 tion at the decomposition surface. The thermal decom- and that of the second confining layer 16 is about 5 x position produces many dislocation loops in the area of 45 1017/cm3, while the conductivities of the substrate 18 the deposition surface which in turn degrade minority and electrode 20 are about 5 x 101'/cm3 and 1 x carrier device properties. These discoloration loops are lO'9/cm3 respectively. due to incongruent evaporation at the deposition sur- The semiconductor laser 10 is operated under for- face during the preheating cycle. Therefore, the elimi- ward biased conditions at a threshold current density nation of this thermal decomposition problem would 50 value of about 3400 amperes per centimeter squared or improve semiconductor device performance and would greater. The active layer 12's coherent emission of the in general be most desirable in the semiconductor de- semiconductor laser 10 is at a wavelength of about 7000 vice field. angstroms. The first and second confining layers 14 and 16 are of a higher bandgap energy and lower index of SUMMARY OF THE INVENTION 55 refraction than the active layer 12, so as to provide The present process describes a method of fabricating optical confinement of generated radiation and electri- a 111-V semiconductor device by vapor phase deposi- cal confinement of free carriers generated in the active tion of a semiconductor layer on a deposition body layer 12. whereby the deposition body is preheated to a tempera- In the method of the present invention, prior to de- ture about 40" to 60" C. lower than the deposition tem- M) positing a vapor grown layer onto a substrate or onto a perature. previously grown layer (hereinafter referred to as the deposition body), the deposition body is placed in a BRIEF DESCRIPTION OF THE DRAWINGS preheat zone of a vapor phase growth apparatus for FIG. 1 is a cross-sectional view of a semiconductor approximately 3.5 minutes at a temperature about laser which may be fabricated by the method of the 65 40"-60" C. lower than the temperature of the deposition present invention. zone, Le., the temperature at which the subsequently FIG. 2 is a side view of an apparatus suitable for grown layer is to be deposited. It has been discovered carrying out the method of the present invention. that if the deposition body is preheated to a temperature 4,116,733 3 4 about the same as the temperature of the deposition chamber zone 32, the substrate 18 is flushed with an zone, thermal decomposition occurs at the depositing inert gas such as hydrogen.
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