Influence of carrier localization on the carrier transport in InAs/InAsSb type-II superlattices

InAs/InAsSb type-II superlattices (T2SLs) have attracted much interest for infrared detection since they demonstrated longer minority carrier lifetime than the traditional InAs/InGaSb T2SLs, due to the reduced Shockley-Read Hall recombination rate. However, recently a long minority carrier lifetime of 12.8 μs at 15 K is reported and proved to be due to carrier localization below 50 K, indicating that long carrier lifetime may sometimes come from carrier localization. It is therefore worth investigating the carrier transport in InAs/InAsSb T2SLs under the influence of carrier localization so as to evaluate its influence on photodetector device performance. An InAs/InAsSb T2SL photodetector with PIN structure and a cut-off wavelength of 4.7 μm is grown using MBE then fabricated. The photoluminescence (PL) peak shows a blue shift of 2.5 meV when temperature increases from 15 K to 40 K, and the minority carrier lifetime measured by time-resolved PL decreases monotonically from 1.67 μs at 15 K to 0.31 μs at 77 K, revealing that carrier localization occurs at these low temperatures. The surface photovoltage method is used to determine the hole diffusion length in the un-intentionally doped intrinsic layer with experimentally determined absorption coefficients and voltage signals. The extracted hole diffusion length is relatively constant as 0.82 μm at 15 K and 0.75 μm at 77 K, as confirmed by that the experimentally measured responsivity is constant below 77 K. The constant diffusion length can be attribute to the reduced hole mobility by carrier localization, even though the minority carrier lifetime is dramatically increased. More discussions will be present at the conference.