Short/Mid-Wave Two-Band Type-II Superlattice Infrared Heterojunction Phototransistor

We report on a short/mid-wave (SW/MW) two-band type-II InAs/GaSb superlattice infrared heterojunction phototransistor (HPT). The structure consists of two back-to-back HPTs for the SW and MW detections. At 77 K, the 50% cutoff wavelength of the SW and MW HPT is 2.6 and $4.2~\mu \text{m}$ , respectively. When the applied bias voltage is 1.2 V, the responsivity is 213 A/W and the current gain is 611 for the SW band, while for the MW band, the responsivity is 45.2 A/W and the current gain is 377 at bias voltage of 1.3 V. At 1.2 V, the shot noise limited detectivity $D ^{\ast }$ of the SW channel and the MW channel is $1.9\times 10^{11}$ and $1.7\times 10^{9}$ cm ${\cdot }$ Hz ^0.5 /W, respectively.