OE_50200: Compound Semiconductors

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OE_50200 Compound Semiconductors Jim Y.
Chi(???) ???????? National Dong-hua
University, Hualian, Taiwan 2007. 02. 22
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Course reference MIT OpenCourseWare
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Outline

• Crystal Structures
• Bulk crystal growth
• Band structures
• Properties of Semiconductors Si and compounds

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• Points to be covered in Lecture 1
• The families (III-V's, II-VI's, IV-VI's,
  IV-IV's), Eg vs a
• Band structures (E vs k G, L, X minima direct
  vs. indirect gaps)
• Crystal lattices, electrical properties, optical
  properties trends in properties and the periodic
  table. The useful compounds.

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Worldwide Semiconductor Revenue
Worldwide Compound Semiconductor Forecast
Worldwide Compound Semiconductor Revenue
BCC Inc.
Worldwide semiconductor revenue will rise to
255.7 B in 2006, up from 237 B in 2005,
according to iSuppli
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mm

• The number of transistors that can be
  inexpensively placed on an integrated circuit is
  increasing exponentially, doubling approximately
  every two years
• Moore's Law describes this driving force of
  technological and social change in the late 20th
  and early 21st centuries.
• Self-fulfilling prophecy for the industry!
• What is the Moors law for Compound Semiconductor
  technology?
• Whats the Post-Moores law technologies?

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Crystal Structures
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• 4 inches are still used for MEMs and Photonic
  circuits
• GaAs wafers are up to eight inches-one step
  behind Si

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Outline

• Crystal Structures
• Bulk crystal growth
• Band structures
• Properties of Semiconductors Si and compounds

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Band Structures for Electrons and Holes
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Band Structures of Semiconductors Ge, Si, GaAs
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Properties of Common Semiconductors
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Bandstructure of GaN
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Direct and Indirect Bandgap

• Because of the small momentum of photons, the
  optical transition are vertical.
• Direct bandgap materials are more efficient light
  emitter and absorber than indirect bandgap
  material. This properties has consequence on the
  LEDs, solar cells
• hv -gt e h
• Si, Ge, C or their combinations are indirect
  bandgap materials.
• III-V and III-N tend to be direct bandgap
  materials, the exceptions are GaP and AlAs

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Band structure of Diamond Structures (sp3
hybridization)
Angular part of the atomic s and p orbitals

• Conduction band at k0 is S-like with spherical
  symmetry and and the valence band are linear
  combination of P-like states.
• The split-off band (SO), are due to the
  spin-obital interaction of the electrons and the
  nucleus
• The effective mass is

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Why Si is indirect and GaAs direct?
http//www.designers-guide.org/Forum/YaBB.pl?num1
150452919
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Outline

• Crystal Structures
• Bulk crystal growth
• Band structures
• Properties of Semiconductors Si and compounds

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First - ever LED Report
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Outlines
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Si is science and GaAs is the art!!!
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Diamond and Zinc Blend Structures

• Si, Ge, C or their combinations are indirect
  bandgap materials
• III-V and III-N tend to be direct bandgap
  materials, the exceptions are GaP and AlAs

• Different crystal direction will have different
  chemical and physcial properties.
• Orientation dependent etching
• Channeling for ion implantation and diffusion

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Hexagonal Structure -GaN
Zince Blend
Wurtzite
?- Wurzite ?- Zinc Blend

• Wurtzite structure has one axis of the tetrahedra
  longer.
• Wurtzite material does not have central symmetry
  leads to piezo-electric effect in the
  C-direction.
• Miller indices of Wurtzite structure?

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Substrates for Epigrowth
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Epitaxy is the Key for Optoelectronic
Semiconductor Devices
Lattice Constants, Å
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Wavelength Range for Epitaxy Materials
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650
807
400
980
780
1310
1550
GaInAs/InP
InP
AlInGaAs/InP
GaAsSb/GaAs
InGaNAs/GaAs
GaAs
InGaAs/GaAs
hu
AlGaAs/GaAs
Hole levels
QDs
AlGaInP/GaAs
GaInN/GaN
200 400 600 800
1000 1200 1400 1600
Wavelength, nm
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• Points to be covered in Lecture 1
• The families (III-V's, II-VI's, IV-VI's,
  IV-IV's), Eg vs a
• Band structures (E vs k G, L, X minima direct
  vs. indirect gaps)
• Crystal lattices, electrical properties, optical
  properties trends in properties and the periodic
  table. The useful compounds.