MWIR and LWIR HgCdTe Infrared Detectors Operated with Reduced Cooling Requirements

Abstract

In this work, we analyze Auger suppression in HgCdTe alloy-based device structures and determine the operation temperature improvements expected when Auger suppression occurs. We identified critical material (absorber dopant concentration and minority-carrier lifetime) requirements that must be satisfied for optimal performance characteristics. Calculated detectivity values of Auger-suppressed and standard double-layer planar heterostructure (DLPH) devices demonstrate consistently higher maximum backgroundlimited temperatures over a range of cutoff wavelengths and generally higher detectivity values achieved by Auger-suppressed detectors. Furthermore, these devices can operate with comparable performance at up to 100 K higher than DLPH detectors operating at reference temperatures above 100 K. Results of these simulations demonstrate that Auger-suppressed detectors provide a significant advantage over DLPH devices for high-temperature operation and are a viable candidate for thermoelectrically cooled detectors. Experimental dark current-voltage (I-V) characteristics between 120 K and 300 K were fitted using numerical simulations. By fitting the temperaturedependent I-V experimental data, we determined that the observed negative differential resistance (NDR) is due to Auger suppression. More specifically, NDR is attributed to full suppression of Auger-1 processes and partial ($70%) suppression of Auger-7 processes. After Auger suppression, the remaining leakage current is principally limited by the Shockley-Read-Hall recombination component. Part of the leakage current is also due to a residual Auger-7 current in the absorber due to the extrinsic p-type doping level. Analysis and comparison of our theoretical and experimental device results in structures where Auger suppression was realized are also presented.

Numerical Modeling of SRH and Tunneling Mechanisms in High-Operating-Temperature MWIR HgCdTe Photodetectors

“…Composition, doping, and temperature dependence of the electronic, transport, and optical parameters of HgCdTe are described through the models proposed in Ref. 17 5,9) for radiative and Auger lifetimes, where we assume F 12 ¼ 0:2 for the overlap integral of the Bloch functions and c ¼ 6 for the ratio between Auger-7 and Auger-1 intrinsic lifetimes. 22,23 The simulated structures are discretized with a highly customizable meshing tool, generating a denser mesh in regions where high gradients of current density, electric field, free charge density, and material composition are expected.…”

“…Since HOT infrared detectors should preserve at 150 K and above the performance characteristics formerly obtained at substantially lower temperatures (80 K to 100 K), a considerable reduction of the dark current is essential to obtain high sensitivity. [8][9][10][11] Two sets of devices, manufactured with the same nominal structure but different p-doping technologies, are presented in ''Device Fabrication and Experimental Dark Currents'' section, and their experimental dark currents are compared and discussed. In ''Simulation of the Low Reverse Bias Regime'' section, a simulation study of the dark currents demonstrates the favorable effects on Shockley-Read-Hall (SRH) and Auger generationrecombination (GR) rates of avoiding metal-vacancy doping and reducing the acceptor density.…”

Status of long-wave Auger suppressed HgCdTe detectors operating > 200 K

“…The Auger sup− pression is visible by negative differential resistance (NDR) in the reverse−bias current -voltage (I-V) characteristics. Auger GR suppression in active layer is reached by combi− nation of exclusion (P + /p or N + /n) and extraction (N + /p or P + /n) heterojunctions implemented into simple P + /n/N + or P + /p/N + architectures (where p and n stands for slightly p and n−type doping layers respectively) [12][13][14][15][16]. Those P + /p/N + , P + /n/N + configurations have demonstrated signifi− cant suppression of Auger GR mechanisms by reducing the absorber carrier density below thermal equilibrium in re− verse bias condition, however p−type (p) absorber offers better absorption coefficient and lower inherent Auger GR which should improve the detector's performance.…”

Modeling and Simulation of High Operating Temperature MWIR Photo Detector Based on Mercury Cadmium Telluride

“…There is, therefore, a great interest in achieving higher operating temperature infrared systems. The limiting factor for cooling requirements was the dark current in the detector devices [4]. The dark current in HgCdTe (MCT) infrared detectors was limited by Auger processes at near-room temperatures of operation.…”