LAUSR

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 $2.9\times 10^{-5}$ A/cm² under −0.1 V and a zero-bias differential-resistance-area product (R₀A) in excess of $8\times 10^{3}~ \Omega \cdot \text {cm}^{2}$ . 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 $6.4~\mu \text{m}$ at 77 K under zero bias, with a peak responsivity of 0.56 A/W. The corresponding specific detectivity is $7.6\times 10^{11}~\text {cm}\cdot \text {Hz}^{1/2}$ /W. The key device parameters which limit the further optimization of performance are discussed.