MOCVD grown HgCdTe barrier detectors for MWIR high-operating temperature operation

Abstract

In the last decade, new architecture designs such as nBn devices or unipolar barrier photodiodes have been proposed to achieve high-operating temperature (HOT) detectors. This idea has been also implemented in HgCdTe ternary material systems. However, the implementation of this detector structure in an HgCdTe material system is not straightforward due to the existence of a valence band discontinuity (barrier) at the absorber-barrier interface. We report on midwavelength infrared HgCdTe barrier detectors with a zero valence band offset, grown by metal organic chemical vapor deposition on GaAs substrates. The experiments indicate the influence of the barrier on the electrical and optical performances of the p+BpnN+ device. The devices exhibit very low-dark current densities in the range of (2−3)×10−3 A/cm2 at 230 K and a high-current responsivity of about 2 A/W in the wide range of reverse bias voltage. The estimated thermal activation energy of about 0.33 eV is close to the full Hg0.64Cd0.36Te bandgap, which indicates diffusion limited dark currents.