Recombination Processes in InAs/InAsSb Type Ⅱ Strained Layer Superlattice MWIR nBn Detectors

摘要

There is great interest in MWIR Ga-free type Ⅱ strained layer superlattice (T2SLS) nBn detectorsfor background limited photodetectors (BLIP) operating at temperatures higher than InSb (T ≥ 150Kcompared to T≈ 80-90K). Recently, Ting et al. [Proc. SPIE, Vol. 10624, 1062410-1 (2018)] reportedon measurements of the dark current and quantum efficiency (QE) for e-SWIR (λ>1.7 μm), MWIR,and LWIR Ga-free nBn T2SLS detectors. Of particular interest is the reported MWIR nBn T2SLSdata, since the measured dark current and QE provide the opportunity to analyze the measureddetector optoelectronic characteristics using optical properties obtained separately from the holeminority carrier lifetime and optical absorption coefficient data, hence no adjustable parameters. Thegoal is to develop and utilize robust modeling techniques to explain real, measured nBn detector datato understand the technology limitations and the improvements needed to optimize performance anddevice designs. A notable result is the observation that the dark current data under reverse bias (-100mV < bias ≤ 0 mV) obeys the ideal diode equation, where the saturation dark current is in agreementwith the radiative recombination rate obtained from the measured absorption coefficient and a 9 μsShockley-Read-Hall (SRH) lifetime obtained from the measured hole lifetime data. Most importantis that the expected generation-recombination (G-R) space charge current based on the 9 μs SRHlifetime is not observed as expected for an ideal nBn heterojunction detector and that increasingexcess dark currents are observed with decreasing temperature. The in-band external QE measuredat 100K is in the range of 30% and is observed to increase with increasing operating temperaturewhich indicates effects influenced by hole mobility anomalies. In contrast to the above listedobservations, the type Ⅱ Ga-free nBn detector data reported by D. Ting et al. [Appl. Phys. Lett.,113, 021101, 2018] exhibits a hole energy barrier, G-R dark current like characteristics, and bothtemperature/voltage dependent QE.