M. Ershov, A. G. U. Perera and S. G. Matsik
Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303
H. C. Liu
Institute for Microstructural Sciences, National Research Council, Ottawa, Canada
ABSTRACT
The effects of optical interference in quantum-well infrared photodetectors
(QWIPs) caused by reflection of radiation from the metal contact are
investigated. It is shown that interference leads to strong deterioration of
QWIP characteristics (responsivity, noise, and noise equivalent power (NEP) if
signal photocurrent is larger than the dark current or background current. This
is caused by the nonuniform distribution of the photogeneration rate, electric
field, and all other microscopic physical quantities. As a result, the
photocurrent gain and photoionization efficiency are decreased, while the noise
gain is increased with respect to their values for uniform excitation. Several
puzzling experimental effects – a strong increase of the QWIP NEP for
high-power heterodyne operation and temperature dependence of QWIP responsivity
– can be explained by the model described above. © 2000 Elsevier
Science B.V. All Rights Reserved.
Key words: Quantum-well infrared photodetectors; nonlinearity; Optical interference; Responsivity
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