Bandgap-Engineered Mercury Cadmium Telluride Infrared Detector Structures for Reduced Cooling Requirements

State-of-the-art mercury cadmium telluride (HgCdTe) high performance infrared (IR) p-n heterojunction technology remains limited by intrinsic, thermal Auger generation-recombination (C-11.) mechanisms which necessitate strict cooling requirements, and challenges related to processing technology, particularly those associated with achieving stable, controllable in situ p-type doping in molecular beam epitaxy (MBE) grown HgCdTe. These limitations motivate the need to firstly, increase device operating temperatures, and secondly, address material processing issues. This work investigates three alternative HgCdTe IR device architectures as proposed solutions 1) the high operating temperature (HOT) detector, 2) the nBn detector, and 3) the NBnuN detector. The HOT detector is designed to suppress Auger processes, in turn, reducing the detector noise and cryogenic cooling requirements. A simulation study comparing the device behavior and performance metrics of the Auger-suppressed HOT structure to those obtained for the conventional double layer planar heterostructure (DLPH) device predicts the HOT detector can provide a significant advantage over conventional detectors with an increased operating temperature of ∼40-50 K for devices with cutoff wavelengths in the range of 5-12 mum. In a related study, a series of experiments is conducted to examine arsenic (As) deep diffusion in HgCdTe with the goal of achieving controllable low p-type doping in the HOT absorber layer to reduce Auger G-R processes by increasing minority carrier lifetimes. Furthermore, a unipolar, barrier-integrated nBn detector structure is proposed to address the challenges associated with p-type doping in MBE grown HgCdTe. Numerically simulated performance characteristics of the HgCdTe nBn device predict values similar to comparable DLPH structures for a range of temperatures, motivating the experimental demonstration of mid- and long-wave IR HgCdTe nBn detectors. Fabricated nBn detectors successfully exhibit. barrier-influenced current, voltage and photoresponse characteristics, but are limited by perimeter leakage currents which must be resolved in future work. Finally, this work culminates with the simulation study of the novel, hybrid NBnuN structure which addresses both technology limitations by combining the advantages and designs of the Auger-suppressed HOT and unipolar nBn detectors in a single configuration.