InAs/InAsSb Strained-Layer Superlattice Mid-Wavelength Infrared Detector for High-Temperature Operation

Abstract

This paper reports an InAs/InAsSb strained-layer superlattice (SLS) mid-wavelength infrared detector and a focal plane array particularly suited for high-temperature operation. Utilizing the nBn architecture, the detector structure was grown by molecular beam epitaxy and consists of a 5.5 µm thick n-type SLS as the infrared-absorbing element. Through detailed characterization, it was found that the detector exhibits a cut-off wavelength of 5.5 um, a peak external quantum efficiency (without anti-reflection coating) of 56%, and a dark current of 3.4 × 10−4 A/cm2, which is a factor of 9 times Rule 07, at 160 K temperature. It was also found that the quantum efficiency increases with temperature and reaches ~56% at 140 K, which is probably due to the diffusion length being shorter than the absorber thickness at temperatures below 140 K. A 320 × 256 focal plane array was also fabricated and tested, revealing noise equivalent temperature difference of ~10 mK at 80 K with f/2.3 optics and 3 ms integration time. The overall performance indicates that these SLS detectors have the potential to reach the performance comparable to InSb detectors at temperatures higher than 80 K, enabling high-temperature operation.

Influence of Pixel Etching on Electrical and Electro-Optical Performances of a Ga-Free InAs/InAsSb T2SL Barrier Photodetector for Mid-Wave Infrared Imaging

“…Concerning the increment of the QE with the bias, this behavior is due to the increase in depletion width within the AL, allowing for a larger collection of carriers assisted by the electric field. Without anti-reflection coating, QE values as high as 60 % at λ = 3.3 µm were obtained, in agreement with the state-of-the-art QE values [3,6,[8][9]. These QE values could be enhanced by the optimization of the electron and hole wavefunction overlap associated to the fundamental conduction and valence minibands of the T2SL structure by reducing its period thickness while increasing the antimony composition of the InAs/InAsSb heterostructure and keeping the target 5 µm wavelength cut-off [24].…”

“…Compared to the shallow-etched device, the results are much more dispersed but the deep etching seems not to degrade the electrical performance. Indeed, dark current densities vary from 1 × 10 −5 A/cm 2 to 6 × 10 −5 A/cm 2 at 150 K. A dark current density as low as 1 × 10 −5 A/cm 2 is only 7.5 times higher than the one extracted from the MCT Rule 07 [26] and such a value is among the lowest dark current density values recently reported [3,6,8,9]. However, for some devices, forward bias characteristics clearly show a signature of surface leakage current and, combined with the dispersion of results, the deep-etching process seems therefore less robust and less homogeneous than the shallow-etching one.…”

“…In the past ten years, barrier structure (called XBn) has become the standard design of antimonide-based (Sb-based) high-performance cooled infrared (IR) photodetectors, particularly for Ga-free InAsSb bulk and InAs/InAsSb type-II superlattice (T2SL) devices operating in the mid-wave infrared (MWIR, 3-5 µm) spectral domain [1][2][3][4][5][6][7][8][9][10][11].…”

“…Thence, the dark current of such a structure is diffusion limited whatever the temperature and, at a given dark current value, the temperature operation should be enhanced compared to the usual pin photodiode. A temperature operation higher than 140 K has been achieved in the MWIR domain for Ga-free T2SL XBn detector focal plane arrays (FPAs) [3][4][5]8,9]. Specifically, Ting et al [4] reported a 24 µm pitch, 640 × 512 format FPA with a cut-off wavelength of 5.4 µm exhibiting a mean noise equivalent differential temperature (NETD) of 18.5 mK and an NETD operability of 99.7% at a 150 K operating temperature with an f/2 aperture and a 300 K background.…”

Structural, Optical and Electrical Characterizations of Midwave Infrared Ga-Free Type-II InAs/InAsSb Superlattice Barrier Photodetector

“…An alternative to this technology could be the Ga-free InAs/InAs 1-x Sb x T2SL structures [14]. Indeed, an impressive minority carrier lifetime value higher than 3 µs at 80 K in the MWIR domain has been measured [15] and results on Ga-free T2SL detectors have recently been reported by research groups [16][17][18][19][20][21][22][23]. Although this new kind of detector technology operating in the full MWIR domain has recently reached significant performances, it still requires improvements in terms of dark current density values, turn on voltage, quantum efficiency and operation temperature.…”