Extended short wavelength infrared heterojunction phototransistors based on type II superlattices

A two terminal extended short wavelength infrared heterojunction phototransistor based on type-II InAs/AlSb/GaSb on a GaSb substrate is designed, fabricated, and investigated. With the base thickness of 40 nm, the device exhibited a 100% cut-off wavelength of ∼2.3 μm at 300 K. The saturated peak responsivity value is 320.5 A/W at 300 K, under front-side illumination without any antireflection coating. A saturated optical gain of 245 at 300 K was measured. At the same temperature, the device exhibited a collector dark current density (at unity optical gain) and a DC current gain of 7.8 × 10−3 A/cm2 and 1100, respectively. The device exhibited a saturated dark current shot noise limited specific detectivity of 4.9 × 1011 cm·Hz1/2/W at 300 K which remains constant over a broad range of wavelengths and applied biases.