Mid-Wave Infrared InAs/GaSb Type-II Superlattice Photodetector With n-B-p Design Grown on GaAs Substrate

In this paper, we report the direct growth and characterization of a mid-wave infrared InAs/GaSb type-II superlattice n-B-p photodetector on a GaAs substrate. The design consists of an n-doped contact, a wide bandgap unipolar barrier, and a p-doped absorber, which uses photogenerated electron as minority carriers to enjoy the longer electron diffusion length compared with hole diffusion length. At 77 K, the device exhibits a dark current density of 2.9 × 10 -5 A/cm 2 under -0.1 V and a zero-bias differential-resistance-area product (R 0 A) in excess of 8 × 103 Ω · cm 2 . Arrhenius analysis of dark current demonstrates that the dominant mechanism is diffusion at a temperature higher than 130 K. 50% cutoff wavelength of the detector is found at 6.4 μm at 77 K under zero bias, with a peak responsivity of 0.56 A/W. The corresponding specific detectivity is 7.6 × 10 11 cm · Hz 1/2 /W. The key device parameters which limit the further optimization of performance are discussed.