Diffusion-limited dark currents in mid-wave infrared HgCdTe-based nBn structures with Al2O3 passivation

Abstract

We present the results of the study of the dark current in the MWIR nBn structure based on n-Hg1−xCdxTe grown by molecular beam epitaxy on a GaAs (0 1 3) substrate. The CdTe content in the barrier layer is 0.84, and its thickness is 210 nm. To suppress the surface current, passivation with an Al2O3 layer formed by plasma-enhanced atomic layer deposition was used. The dark current density at the temperature of 184 K and the voltage bias of −1 V is 3.1 × 10−6 A cm−2. At temperatures higher than 180 K, the total current through the nBn structure is determined by the diffusion component. In the temperature range of 180–300 K, the dark current values correspond well to the empirical model of Rule 07. These values are comparable with the dark current values for modern mid-infrared barrier detectors based on MOCVD HgCdTe and III–V materials. The studied nBn structures have lower dark currents than the previously described analogues based on MBE HgCdTe, which may be associated with high-quality passivation of the side walls of the mesa structure.