Effects of layer thickness and alloy composition on carrier lifetimes in mid-wave infrared InAs/InAsSb superlattices

Abstract

Measurements of carrier recombination rates using a time-resolved pump-probe technique are reported for mid-wave infrared InAs/InAs1−xSbx type-2 superlattices (T2SLs). By engineering the layer widths and alloy compositions, a 16 K band-gap of ≃235 ± 10 meV was achieved for all five unintentionally doped T2SLs. Carrier lifetimes were determined by fitting a rate equation model to the density dependent data. Minority carrier lifetimes as long as 10 μs were measured. On the other hand, the Auger rates for all the InAs/InAsSb T2SLs were significantly larger than those previously measured for InAs/GaSb T2SLs. The minority carrier and Auger lifetimes were observed to generally increase with increasing antimony content and decreasing layer thickness.

Evidence of a Shockley-Read-Hall Defect State Independent of Band-Edge Energy inInAs/In(As,Sb)Type-II Superlattices

“…Samples are grown by molecular beam epitaxy using previously described techniques [6,9,10,13]. For all seven samples, the epitaxial layers consist of a GaSb buffer layer, a bottom 100-nm Al(As,Sb) barrier layer, an unintentionally doped and nominally 4-μm-thick T2SL absorber layer, a top 100-nm Al(As,Sb) barrier layer, and a 150-nm In(As,Sb) cap layer.…”

“…Temperature-and carrier-density-dependent studies on MWIR InAs=InðAs; SbÞ T2SLs have shown that SRH recombination limits the MC carrier lifetime at low temperatures and low-injection carrier densities [5,6,[8][9][10]13]. The mid-band-gap SRH recombination centers identified in MWIR InAs=InðAs; SbÞ T2SLs have been previously reported to be at an energy approximately 250 meV below the valence-band edge of bulk GaSb [5,9].…”

“…InAs=InðAs; SbÞ type-II superlattices (T2SLs) were proposed as an alternative material to Hg(Cd,Te) for infrared (IR) detection in 1985 [1]. Since then, many different designs and growth methods have been studied to improve the structural and optical properties of these T2SLs to realize next-generation IR detectors and focal plane arrays [2][3][4][5][6][7][8][9][10][11]. Improvements in detectivity and responsivity have been the main focus of T2SL photodetector development; however Hg(Cd,Te) continues to set the goals for dark current and sensitivity [12].…”

“…Improvements in detectivity and responsivity have been the main focus of T2SL photodetector development; however Hg(Cd,Te) continues to set the goals for dark current and sensitivity [12]. Improvements in T2SL detector performance depend critically on the minority-carrier (MC) lifetime, which currently is controlled by flaw-related Shockley-Read-Hall (SRH) recombination [5,6,[8][9][10]13] at typical operating temperatures. Previously, InAs=InðAs; SbÞ T2SLs have been shown to have MC lifetimes of approximately 10 μs in the midwave infrared (MWIR) [6,13] and hundreds of nanoseconds in the long-wave infrared (LWIR) [14,15], with Auger coefficients reported between 1 and 5 × 10 −26 cm 6 =s for MWIR [6,10] and low 10 −25 cm 6 =s for LWIR [15].…”

Probing the free-carrier absorption in multi-layer black phosphorus

“…A fast, transient increase in differential-transmission signal is observed with a measured response time of 1.4 ps and 2 ps for 2.4 µm and 3.2 µm probe wavelengths, respectively. These timescales characterize the rate at which pump-induced hot carriers thermalize and relax to the band edge 20 . When the probe wavelength continues to increase, the differentialtransmission signal becomes progressively slower, and when the probe wavelength is extended to 4 µm, just above the bandgap, the Pauli-blocking transient persists for nearly 90 ps.…”