Theory and Experiment of Antimony-Based Type-Ii Superlattice Infrared Photodetectors
Mou, Shin
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https://hdl.handle.net/2142/81037
Description
Title
Theory and Experiment of Antimony-Based Type-Ii Superlattice Infrared Photodetectors
Author(s)
Mou, Shin
Issue Date
2007
Doctoral Committee Chair(s)
Chuang, Shun-Lien
Department of Study
Electrical and Computer Engineering
Discipline
Electrical and Computer Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Language
eng
Abstract
There is currently considerable interest in InAs/InGaSb type-II superlattices because of their broken-gap type-II band alignment, which forms spatially indirect band gaps in the range of 3--30 mum. Combining the advantages of III-V epitaxial growth techniques and high sensitivity to normal incident light, the InAs/InGaSb superlattice is a promising material system for the next generation of mid-infrared photodetector focal plane arrays (FPAs). In order to understand the underlying physics and to improve the device performance of this emerging technique, InAs/InGaSb superlattice photodetectors are studied theoretically and experimentally in this dissertation. First, an eight-band k · p method is developed to model the band structures and absorption coefficient. The calculated absorption coefficient spectra agree very well with our experimental curves, validating the effectiveness of the eight-band k · p method. Second, quantum efficiency (QE), an important figure of merit for infrared photodetectors, is analyzed by an analytical model based on absorption coefficient and transport parameters (e.g., minority carrier diffusion length) obtained by electron beam induced current (EBIC) technique. By successfully modeling the QE of InAs/GaSb superlattice photodiodes, we ensure that the depletion region in InAs/GaSb superlattice photodiodes is effective in collecting the photoexcited carriers. Understanding the dark current mechanisms of InAs/GaSb superlattice photodiodes is another important task when the surface leakage current is detrimental. We use an analytical model, which explains successfully the measured I-V curves. With the observation of a sinh(qV/4KT) dependence under small forward bias, a surface channel current model originally developed by Sah is used to explain the surface leakage current of InAs/GaSb superlattice photodiodes for the first time. Besides the conventional photodiodes, we take advantage of the InAs-(In)GaSb-Al(In)Sb nearly lattice-matched system to design novel antimony-based type-II photodetectors based on our eight-band k · p method. After interband cascade detectors with promising room temperature performance (dynamic impedance and area product (R0A) equals to 22 Ocm2 at 300 K) are obtained, a new design for interband tunneling detectors is introduced. With a thicker active region, the QE of interband tunneling detectors is improved more than five times compared to that of interband cascade detectors.
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