Optoelectronics and Optical Communication FFFN25/FYST50 Dan Hessman, Solid State Physics Cord Arnold, Atomic Physics Optoelectronics The application of electronic devices that source, detect and control light. (Electronic devices = semiconductor devices) Optical Communication The use of light to transport information. Practical Info Lectures Mondays 13-15 and Thursdays 8-10 K404 (or Rydberg) H221, H421 Rydberg H442,H443 Calculus exercises Fridays 13-15 (2 Feb: 15-17) H221 (H421) K404 Cord Arnold Dan Hessman Lab exercises - The Diode Laser (Q131) Q131 - Fiber Optics (H443) - CCD & CMOS Cameras (H442) Email with instructions for signing up Practical info Literature • Fundamentals of Photonics, B. E. A. Saleh and M. C. Teich • ~880kr @ KFS • Can be found as e-book via the University library • Lecture notes • Hand out material. On website, password protected Exam • 16/3 MA10, 14.00-19.00 • Book allowed, e-book not allowed! Course Outline Week 1: Optical Processes & Semiconductor Optics Week 2: Semiconductor Photon Sources Week 3: Fiber waveguides Week 4: Semiconductor Photon Detectors Week 5: Fiber communication Week 6: Cameras and Photovoltaics Week 7: Coherent communication + repetition Semiconductors Ch 16 12.345*2/*6/ 6. Halvledare !"#$%"#&'()(%*'$%#(%*%$#+,$-.#/.#%,,#,0(($123(04,#'",'(#%(%3,$/"%$#&'$#%520,%$',+#,0((#(%*"0"4+6'"7 *%,8#)0(3%,#3'"#+3%#,#%5#4%"/.#9::)1$."0"4#%((%$#6%(;+"0"4<#!(%3,$/"%$"'#0#*%,#,1.(04%"#,/..' 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Semiconductors for which this is not the case are known as indirect-bandgap materials. As is evident in Fig. 16.1-5, GaAs is a direct-bandgap semiconductor whereas Si is an indirect-bandgap semiconductor. The distinction is important because a transition between the bottom of the conduction band and the top of the valence band in an indirect-bandgap semiconductor must accommodate a substantial change in the momentum of the electron. It will be shown subsequently that direct-bandgap semiconductors such as GaAs are efficient photon emitters, whereas indirect-bandgap semiconductors such as Si cannot serve as efficient light emitters under ordinary circumstances. B. Semiconductor Materials Figure 16.1-6 reproduces the section of the periodic table that comprises most of the elements important in semiconductorSemiconductorelectronics and photonics. Both elemental and compound semiconductorsmaterialsplay crucial roles in these technologies. • Group IV: Si, Ge Indirect; Detectors, CCD, photovoltaics • Group III-V: GaP, GaAs, InGaAsP… LEDs, lasers, detectors • GroupGas III-N: GaN, InGaN… Blue (&white) LEDs, UV lasers D Liquid • Group II-VI: HgCdTe… IR camerasSolid Figure 16.1-6 Section ofThethe periodic periodictable relating tableto semiconductors. Elements indicated in blue, yellow, and silver take the form of gases, liquids, and solids, respectively, at room temperature. The full periodic table is displayed(fromin Fig. a semiconductor13.1-3. physicist’s view) We proceed to discuss elemental, binary, ternary, and quaternary semiconductors in turn, and then consider doped semiconductors. Elemental Silicon (Si) and germanium (Ge) are important elemental Semiconductors semiconductors in column IV of the periodic table. Virtually all commercial electronic integrated circuits and devices are fabricated using Si. Both Si and Ge also find widespread use in photonics, principally as photodetectors. These materials have traditionally not been used for the fabrication of light emitters because of their indirect bandgaps. However, some forms of Si are viable as light emitters and silicon photonics has come to the fore. The basic properties of Si and Ge are provided in Table 16.1-2. How do we produce semiconductor structures? Epitaxy Homostructure Heterostructure Add one atom layer at a Just one material Combinaons of materials me to substrate wafer Lace matching important! GaAs p AlGaAs GaAs GaAs n AlGaAs Wafer Epitaxy machine Reactor cell 16.1 SEMICONDUCTORS 637 0.5 AIN 0.2 0.6 2.0 E E 0.7 :::i. OJ 0.3 0.8 ...-'"( 4 ...-'"( OJ ..c lLJ ..c >. >. bO 1.0 • Si 3 0.4 1.2 g- 1.0 g- 0.5 bO g- bO 0.6 g- -g bO -g 2 bO 2.0 ] -g 0.5 P:::l 1.0 3.0 2.0 10 0 0 5.4 5.6 5.8 6.0 6.2 6.4 6.6 3.0 3.1 3.2 3.3 3.4 3.5 Lattice constant (A) Lattice constant (A) (a) (b) 16.1 SEMICONDUCTORS 637 Figure 16.1-7 Bandgap energies, bandgap wavelengths, and lattice constants for Si, Ge, SiC, and 12 III-V binary compounds. Solid and dashed curves represent direct-bandgap and indirect- bandgap compositions, respectively. A material0.5 may have AINa direct bandgap for one mixing ratio0.2 and an indirect bandgap for a different mixing ratio. Ternary materials are represented along the line that joins two binary compounds. A quaternary0.6 compound is represented by the area formed by its 2.0 binary components. (a) Inl-xGaxAsl-yPy is represented by the stippled area with vertices at InP, 0.7 E E InAs, GaAs, and GaP, while (AlxGal-x)ylnl-yP is represented by the shaded area with vertices:::i. at OJ 0.3 AlP, InP, and GaP. Both are important quaternary0.8 ...-'"( compounds,4 the former in the near infrared...-'"( and OJ ..c lLJ ..c >.the latter in the visible. AlxGal-xAs is represented>. by points along the line connecting GaAsbOand 1.0 AlAs.• Si As x varies from 0 to 1, the point moves along3 the line from GaAs and AlAs. Since 0.4this line 1.2 g- is1.0nearly vertical, AlxGal-xAs is lattice matchedg-to GaAs. (b) Although the III-nitride compound0.5 bO InxGal-xN can, in principle, be compositionallyg- tunedbO to accommodate the entire visible spectrum,0.6 g- -g bO -g 2 bO this material becomes increasingly difficult2.0 to] grow as the composition of In becomes appreciable.-g 0.5 P:::l 1.0 InxGal-xN is principally used in the green,3.0 blue, and violet spectral regions, while AlxGal-xN and AlxlnyGal-x_yN serve the ultraviolet region. All compositions of these III-Nitride compounds2.0 are direct-bandgap semiconductors. 10 0 0 5.4 5.6 5.8 6.0 6.2 6.4 6.6 3.0 3.1 3.2 3.3 3.4 3.5 Lattice constant (A) Lattice constant (A) (a) (b) ZnS 3.5 Figure 16.1-7 Bandgap energies, bandgap wavelengths, and lattice constants for Si, Ge, SiC, 0.4 • Group IV: Si, Ge and 12 III-3.0 V binary compounds. Solid and dashed curves represent direct-bandgap and indirect- bandgap compositions,ZnSe respectively. A material mayE haveIndirect;a direct bandgapDetectors,for one CCD,mixing photovoltaicsratio and >' 2.5 CdS ZnTe 0.5 3 Ol an indirect bandgap for a different mixing ratio....-'"( Ternary materials are represented along the line lLJOl 2.0 0.6 ..c Figure 16.1-8 Bandgap energies, bandgap that joins>. two binary compounds. A quaternary bOcompound• Groupis represented III-V: GaP,by theGaAs,area InGaAsP…formed by its 0.7 c:: wavelengths, and lattice constants for various binary components.1.5 (a) Inl-xGaxAsl-yPy is representedLEDs,by the lasers,stippled detectorsarea with vertices at InP, > II-VI semiconductors (HgSe and HgTe are InAs, GaAs,g. and GaP, while (AlxGal-x)ylnl-yP1.0 is represented by the shaded area with vertices at bO 1.0 1.2 g. semimetals with small negative bandgaps). AlP, InP,] and GaP. Both are important quaternarybJ) compounds, the former in the near infrared and P:::l 2.0 "0 • GroupHgTe and III-N:CdTe GaN,are nearly InGaN…lattice matched, the latter0.5in the visible. AlxGal-xAs is represented§ by points along the line connecting GaAs and P:::l Blueas evidenced (&white)by LEDs,the vertical UV lasersline connect- 10 AlAs.