Mid-wave infrared HgCdTe nBn photodetector

Abstract

A unipolar, barrier-integrated HgCdTe nBn photodetector with all n-type doping and a type-I band lineup is experimentally demonstrated. Planar mid-wave infrared (MWIR) nBn devices exhibit current-voltage (I-V) characteristics that are consistent with band inversion in reverse bias, indicating a barrier-influenced behavior. Dark current saturation is observed beyond a reverse bias of approximately −0.8 V. Bias-dependent photoresponse is observed in the mid-wave infrared with a cut-off wavelength around 5.7 μm. Numerical modeling based on experimental results predicts an internal peak quantum efficiency of approximately 66%.

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

“…In addition, having taken the difference in the absorber's composition into consideration, we may assume that the presented results coincide with these published by Velicu et al 17,28 Comparing the nB n n and nB n p detectors, it is clearly evident that the SRH contribution is totally suppressed for the n-type absorber structures (diffusion limited), while the p-type absorber architecture exhibits a twoslope behavior with a crossover temperature estimated at the level of T c = 227 K. Both nB n nn + and nB n pn + detectors are diffusion limited (one-slope behavior). Figure 19 compares the R 0 A (k B T/q/J s ; V = 1 mV for BIRD structures) product for nB n n, nB n nn + , and nB n nN + (the N + layer, similarly to the barrier, consists of two sublayers-the very first one fitted with a graded composition to the absorber and the second with x = 0.4) versus the values given by Martyniuk, Gawron, and Rogalski 3316 ''Rule 07,'' being a simple means to compare mercury cadmium telluride (MCT) IR detectors.…”

“…Figure 18 shows the simulated J DARK versus the operating temperature for the MWIR BIRD HgCdTe structures (k c = 5.2 lm, T = 200 K) in comparison with experimental dark current densities for the following detectors: InAs/GaSb with AlGaSb barrier T2SL nB p n (k c = 5.4 lm, T = 230 K), InAsSb with AlAsSb barrier (k c = 5.05 lm, T = 200 K), and the HOT HgCdTe nB n n detector (x = 0.3). 17,[28][29][30] The particular significance of the incorporation of the extra barrier for carriers (n + ) in the BIRD nB n nn + structures versus the single barrier (potential majority-carrier blocking) is clearly evident from the J DARK decrease from 3 A/cm 2 to 7 9 10 À3 A/cm 2 and 40 A/cm 2 to 3 A/cm 2 for T = 200 K and T = 300 K, respectively. Proper contact layer arrangement increases the operating temperature by close to 75 K for V = 0.4 V. The absorber's p-type doping (assuming the same level of doping N D = N A = 10 14 cm À3 ) leads to a further decrease of J DARK to the level of 4 9 10 À3 A/cm 2 and 2 A/cm 2 for T = 200 K and T = 300 K, respectively.…”

“…Figure 18 shows the simulated J DARK versus the operating temperature for the MWIR BIRD HgCdTe structures (k c = 5.2 lm, T = 200 K) in comparison with experimental dark current densities for the following detectors: InAs/GaSb with AlGaSb barrier T2SL nB p n (k c = 5.4 lm, T = 230 K), InAsSb with AlAsSb barrier (k c = 5.05 lm, T = 200 K), and the HOT HgCdTe nB n n detector (x = 0.3). 17,[28][29][30] The particular significance of the incorporation of the extra barrier for carriers (n + ) in the BIRD nB n nn + structures versus the single barrier (potential majority-carrier blocking) is clearly evident from the J DARK decrease from 3 A/cm 2 to 7 9 10 À3 A/cm 2 In addition, having taken the difference in the absorber's composition into consideration, we may assume that the presented results coincide with these published by Velicu et al 17,28 Comparing the nB n n and nB n p detectors, it is clearly evident that the SRH contribution is totally suppressed for the n-type absorber structures (diffusion limited), while the p-type absorber architecture exhibits a twoslope behavior with a crossover temperature estimated at the level of T c = 227 K. Both nB n nn + and nB n pn + detectors are diffusion limited (one-slope behavior). Figure 19 compares the R 0 A (k B T/q/J s ; V = 1 mV for BIRD structures) product for nB n n, nB n nn + , and nB n nN + (the N + layer, similarly to the barrier, consists of two sublayers-the very first one fitted with a graded composition to the absorber and the second with x = 0.4) versus the values given by ''Rule 07,'' being a simple means to compare mercury cadmium telluride (MCT) IR detectors.…”

The Numerical–Experimental Enhanced Analysis of HOT MCT Barrier Infrared Detectors

“…A non-zero valence band offset in MCT-based barrier detector structures is the key item limiting their performance, [6][7][8][13][14][15] because holes generated by an optical absorption are not able to overcome the valence band energy barrier. Relatively high bias is required to be applied to collect photogenerated carriers.…”

“…[1][2][3][4][5][6][7][8] Dark current caused by Shockley Hall Read (SHR) generation-recombination (G-R) processes associated with metal vacancies and dislocations is a very important issue. These SHR mechanisms are intensified by a trap-assisted tunneling (TAT) process.…”