Bias-switchable dual-band HgCdTe infrared photodetector

The feasibility of an all molecular-beam epitaxially (MBE) grown, bias-switchable, dual-band HgCdTe detector is demonstrated. Detection in the midwavelength infrared (MWIR) band only or the long-wavelength band (LWIR) only is accomplished by the proper selection of detector bias in the ≥±100 mV range. The devices were all grown in situ by the MBE on CdZnTe or GaAs substrates and consisted of three intentionally doped layers in an n–p–n sequence. At 77 K the floating base two terminal devices responded to the ∼4.9–8 μm spectral band with the application of ≥−100 mV to the bottom contact and to the ∼2.1–4.9 μm band with the application of ≥0 mV. Quantum efficiency depended on bias with a maximum of 59% for LWIR and 66% for MWIR wavelengths at −150 mV and ≥0 mV, respectively. The operation of the dual-band detector is discussed. Significant design differences between the heterojunction phototransistor and the dual-band detector are noted.