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In this thesis, we present a theoretical model for bound-to-
continuum state intersubband optical transition so as to
provide a detail design rule for bound-to-continuum multiple
quantum well infrared photodetector. The positions of subband
levels will directly decide the absorption wavelength of
photodetector, we develop an energy- and spatial-dependent
effective mass approach method to calculate the subband
structures of bound states and continuum states. Furthermore,
by our theoretical calculation results above, we can understand
how the absorption peak wavelength and bandwidth vary with the
quantum well parameters (such as well width, barrier height and
barrier width). As shown in the theoretical calculations, we
note that the bound-to-continuum state intersubband optical
transition has smaller optical absorption coefficient than
bound-to-bound state intersubband optical transition, and these
extended state detectors of the front are based on hot-electron
transport above the quantum well barriers, the photoexcited
electrons do not have to escape from the quantum well via
tunneling. Thus the thickness of the barriers can be
significantly increased, dramatically reducing the dark
current. This is the reason why the bound-to-continuum multiple
quantum well infrared photodetectors have larger responsivity
than bound-to-bound multiple quantum well infrared
photodetectors. The theoretical analysis included optical
absorption, quantum efficiency, responsivity, and detectivity
allow a better optimization of the QWIP performance.
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