Theory and experiments of type-II superlattice infrared photodetectors
Qiao, Pengfei
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https://hdl.handle.net/2142/34583
Description
Title
Theory and experiments of type-II superlattice infrared photodetectors
Author(s)
Qiao, Pengfei
Issue Date
2012-09-18T21:26:40Z
Director of Research (if dissertation) or Advisor (if thesis)
Chuang, Shun-Lien
Department of Study
Electrical & Computer Eng
Discipline
Electrical & Computer Engr
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
Type-II superlattice
Infrared Photodetectors
Band structures
k.p method
Infrared spectroscopy
Interfacial effect
Abstract
The InAs/GaSb type-II superlattices have drawn extensive research interest in the past few decades. The type-II band alignment in this material system provides a long cutoff wavelength and a wide optical tunable range in the mid-infrared regime. Photodetectors based on type-II superlattices are theoretically predicted to surpass the performance of those based on the commercialized HgCdTe II-VI system. An electronic band structure model is formulated based on the 8-band k · p method. The absorption and quantum efficiency spectra are calculated, showing good agreement with experimental data. The interfacial effect in type-II superlattices is investigated. It is shown that the interfacial layers can be employed not only to balance lattice strain and reduce detector dark current, but also to simultaneously increase the cutoff wavelength and quantum efficiency. State-of-art interface controlled samples designed for comparison study are processed into devices. The device performance is characterized electrically by dark current measurements, and optically by Fourier transform infrared spectroscopy. Significant improvement of device performance by interface control is demonstrated, which agrees with the prediction by the theoretical model.
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