Low Temperature Noise Measurement of an InAs/GaSb-based nBn MWIR Detector.

摘要

Recent experiments on conventional p-on-n and n-on-p Type II superlattices (SLS) infrared detectors still indicate larger than theoretically predicted dark current densities, despite the well known suppression of the Auger recombination mechanism. Rather, dark current in SLS is thought to still be limited by trap-assisted tunneling in the depletion region and surface leakage currents resulting from lack of fully passivated mesa sidewalls. An emerging infrared detector technology utilizing a unipolar, single-band barrier design, the so-called nBn architecture, potentially suppresses these remaining noise current mechanisms. In this report, measurements of the noise current spectral density of a mid-wave infrared nBn detector composed of a type-II InAs/GaSb strain layer superlattice (SLS) absorber (n) and contact (n) layers with an AlGaSb barrier (B), under low-temperature, low-background conditions are presented. Here, noise was measured using a transimpedance amplifier incorporating a dewar-mounted feedback resistor RF and source-follower MOSFET, both held at 77 K. This configuration confines high detector impedance issues to the dewar, minimizes Johnson noise due to the electronics, and enhances bandwidth by reducing stray capacitance. Features of the detector's noise spectrums at different bias are examined.