Lecture_5

Lecture_5 - Epitaxial growth of heterostructures Need to...

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1 Prof. J. S. Harris 1 EE243. Semiconductor Optoelectronic Devices (Winter 2010) Need to grow layers, often very thin, with different materials, alloy compositions and doping Three main techniques 1. Liquid phase epitaxy (LPE) 2. Metal organic vapor phase epitaxy (MO-VPE) 3. Molecular beam epitaxy (MBE) Basic epitaxial concept Start with substrate of bulk semiconductor (e.g., GaAs or InP) polished to a Fat surface (a wafer), with a particular crystal orientation (e.g., (100) x direction) Then grow thin layers epitaxially on the substrate (i.e., with a high-quality crystalline structure based on that of the substrate template). Epitaxial growth of heterostructures Prof. J. S. Harris 2 EE243. Semiconductor Optoelectronic Devices (Winter 2010) Comparison of Electronics and Photonics Si/SiO 2 /PolySi Si/SiO 2 /PolySi Si/SiO 2 /PolySi GaAs, GaP, GaSb, InP, InAs, InSb, AlAs, GaN, AlN Si/SiO 2 /PolySi Si/SiO 2 /PolySi Si electronics is a processing based technology Photonics is a materials based technology GaAs x P 1-x , Al x Ga 1-x As, In x Ga 1-x P, In x Ga 1-x As, Al x Ga 1-x Sb, Al x Ga 1-x N, Ga x In 1-x N-- Ternary Alloys Si/SiO 2 /PolySi In x Ga 1-x As y P 1-y , Al x In y Ga 1-x-y As, In x Ga 1-x As y Sb 1-y , In x Ga 1-x N y As 1-y -- Quaternary Alloys In x Ga 1-x N y As 1-y-z Sb z -- Quinary Alloy Si/SiO 2 /PolySi Si/SiO 2 /PolySi Electronics Photonics
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2 Prof. J. S. Harris 3 EE243. Semiconductor Optoelectronic Devices (Winter 2010) Technologically Available Materials InAs AlSb GaSb Ge BULK SLE (Ge) α -SiC InSb CdTe InN GaN AlN ZnS MgSe CdS AlP CdSe ZnTe ZnSe GaAs GaP AlAs InP Si Lattice Constant ( Å ) (.41 μ m) (.62 μ m) 6.0 4.0 3.0 2.0 1.0 3.0 3.2 3.4 5.4 5.6 5.8 6.0 6.2 6.4 Bandgap energy (eV) (1.24 μ m) Visible Spectrum (.31 μ m) (.21 μ m) Prof. J. S. Harris 4 EE243. Semiconductor Optoelectronic Devices (Winter 2010) Liquid-solid phase diagram for GaAs Growth regions of III-V compounds
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3 Prof. J. S. Harris 5 EE243. Semiconductor Optoelectronic Devices (Winter 2010) Basic concept of LPE-- Thermodynamic equilibrium growth Pass a saturated melt of compound (As in Ga) to be grown over surface of substrate and reduce the temperature, which reduces the solubility of As and results in deposition of GaAs horizontal growth technique substrate is pulled in sequence under several different melts to grow a multiple layer structure LPE can successfully and inexpensively grow heterostructures, but precise control over thickness, surface morphology and formation of very abrupt interfaces between materials are difFcult. Liquid phase epitaxy Prof. J. S. Harris 6 EE243. Semiconductor Optoelectronic Devices (Winter 2010) Strengths Thermal equilibrium growth--very low native defect density high radiative efFciency-excellent lasers and LEDs Simple low cost equipment and high thruput No toxic gases and easily handled solids Weaknesses Poor surface/interface morphology Graded heterojunctions-both doping and composition
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This note was uploaded on 06/05/2010 for the course EE 243 taught by Professor Harris,j during the Winter '10 term at Stanford.

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Lecture_5 - Epitaxial growth of heterostructures Need to...

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