Heterostructures Optoelectronic Devices n Light generation in semiconductor

Heterostructures & Optoelectronic Devices n Light generation in semiconductor n Light emission diode (LED) n Semiconductor laser n Heterojunction transistors n Photo-detector

Compound Semiconduc tor Device Market

Light Emission in Semiconductors E conduction electron band - h Band gap valence band + Electron-hole recombination hole Si: Eg = 1. 1 e. V Ga. As: Eg = 1. 4 e. V, = 880 nm Al. As: Eg = 2. 2 e. V, = 565 nm Si: indirect bandgap, ineffective Ga. As: direct bandgap, effective

Electron. Hole Recombinati on and photon If the electron-hole Energy recombination occurs not at the minimum gap point, the emitted photon can have a higher energy. When the recombination involves an impurity state in the gap, lower-energy photon is generated. h > Eg

Light Emission Diode Simple PN Junction LED More efficient heterojunction LED

Lattice Matching in Heteroepitaxy

Semiconductor Laser Lateral confinement by proper electrode design

Heterojunction and HEMT Band Offset High electron-mobility transistor (HEMT) with electron gas from the heavilydoped Al. Ga. As layer moving in the undoped Ga. As channel

Quantum Well and Superlattice Bound states in quantum well to mini-band in superlattice Adjustable bandgap Strained superlattice

III-V Nitride Optoelectronic Devices (see: S. C. Jain et al. , J. Appl. Phys. 87 (2000) 965)

III-V Nitride Optoelectronic Devices Ga. N on sapphire with an Al. N buffer layer Ga. N-In. Ga. N DH LED

Large-scale application of LED

Photodetector E conduction electron band - h Band gap valence band + Reverse biased! Electron-hole generation hole Si: Eg = 1. 1 e. V, c= 1130 nm Simple detector: conductivity increase of semiconductor when illuminated. P-I-N photo-detector: low dark current, quick response.