Stacked multijunction photodetectors of long-wavelength radiation

Uncooled, long-wavelength photovoltaic detectors suffer from poor quantum efficiency and low differential resistance. The problem can be solved by the use of stacked, multiple heterojunction-photovoltaic cells with thin absorber regions. We report here numerical simulation and optimization of the stacked, multiple Hg_1−xCd_xTe heterojunction cells used for detection of 10.6-μm infrared (IR) radiation, operating as zero-bias photovoltaic devices or Auger-suppressed photodiodes. It is shown that the devices can be used as high-performance and fast-response detectors of long-wavelength radiation operating at ambient temperature with detectivities larger by more than one order of magnitude than that of the present practical devices.