Theoretical Modeling of HOT HgCdTe Barrier Detectors for the Mid-Wave Infrared Range

Abstract

This paper reports on theoretical modeling of medium-wavelength infrared HgCdTe barrier infrared detector (BIRD) photoelectrical performance. BIRD HgCdTe detectors were simulated with the commercially available software APSYS. Detailed analysis of the detector performance such as dark current, photocurrent, resistance-area product, detectivity versus applied bias, operating temperature, and structural parameters (absorber doping, barrier composition) was performed to determine the optimal operating conditions. It is shown that higher operation temperature conditions achievable with commonly used thermoelectric coolers allow detectivities of D = 9.5 9 10 10 cmHz 1/2 /W and D * = 1.5 9 10 11 cmHz 1/2 /W at T = 200 K to be obtained for the correct absorber doping for nB n nn + and nB n pn + , respectively. R 0 A for the nB n nn + detector was found to range from 200 X cm 2 to 0.6 X cm 2 at T = 200 K to 300 K, respectively.Key words: HgCdTe, unipolar barrier, nB n n(p), nB n n(p)n + , Auger suppression, photoelectric gain INTRODUCTIONPhotodetectors designed for the mid-wave infrared (MWIR, 3 lm to 5 lm) region meeting the requirements for higher operation temperature (HOT) conditions are important in a variety of civilian and military applications. The key condition which must be fulfilled to design a HOT IR detector is to achieve both low dark current and high quantum efficiency (QE). In standard p-n MWIR photodiodes operating under HOT conditions, the dark current is mostly produced by the Shockley-ReadHall (SRH) generation-recombination (GR) process, Auger, and both: band-to-band (BTB)/trap-assisted tunneling (TAT). [1][2][3] Unfavorable SRH and leakage current components can be suppressed by appropriate selection of barriers (wide-energy-gap materials) incorporated into the detector structure. 4 The barrier selection plays a decisive role due to the lattice constant matching of the detector's constituent layers, the barrier height in both conduction and valence bands (connected directly to the band alignment) being difficult to control from a technological viewpoint.Currently, among barrier IR detectors (BIRDs), the leading position is occupied by devices called unipolar barrier infrared detectors (UBIRDs). A III B V family compounds emerged to play a dominant role in the design of UBIRDs due to a nearly zero band offset in the valence band (e.g., GaSb, InAs 1Àz Sb z cap layers, InAs 1Ày Sb y active region, AlAs 1Àx Sb x barrier). 5 Type II superlattices (T2SLs) of InAs/GaSb with AlGaSb/T2SL barriers (with tunneling and inherited Auger GR process suppression) and more sophisticated structures, such as the ''W'' (InAs/GaInSb/InAs/AlGaInSb), ''M'' (GaSb/ InAs/GaSb/AlSb), and recently presented ''N'' (AlSb/ GaSb/InAs) structures, have also shown promise for HOT conditions. 6-10 The success of T2SLs has resulted from the unique inherited capabilities of the new artificial material with completely different physical properties in comparison with the constituent layers and the nearly zero valence band offsets leading ...

Theoretical Study of Midwave Infrared HgCdTe nBn Detectors Operating at Elevated Temperatures

“…Specific equations and relationships used for calculation of carrier lifetimes and recombination rates are detailed in the Appendix I and Table I. The model was validated by fitting the calculated current-voltage characteristics of the p-n photodiode device to those of established experimental measurements [23][24][25][26] and models were developed on the basis of measured data [23,27,28]. Furthermore, the generation-recombination rates, and mobility values obtained from 1D modeling were compared with analytical models and available published data for HgCdTe with x=0.30 [28,29] .…”

Design and Development of Two-Dimensional Strained Layer Superlattice (SLS) Detector Arrays for IR Applications

“…This type of architecture is preferable when a large barrier in the conduction band offset is not achievable, allowing for zero bias operation [89]. …”

Theoretical Aspects of Minority Carrier Extraction in Unipolar Barrier Infrared Detectors

“…We note there has been extensive and detailed theoretical modeling and analysis of the nBn structure in the literature. [25][26][27][28][29] Here we concentrate on unintended hole barriers which can hinder minority carrier collection.…”