Temperature-dependent optical measurements of the dominant recombination mechanisms in InAs/InAsSb type-2 superlattices

Abstract

Temperature-dependent measurements of carrier recombination rates using a time-resolved optical pump-probe technique are reported for mid-wave infrared InAs/InAs 1Àx Sb x type-2 superlattices (T2SLs). By engineering the layer widths and alloy compositions, a 16 K band-gap of $235 6 10 meV was achieved for five unintentionally and four intentionally doped T2SLs. Carrier lifetimes were determined by fitting lifetime models based on Shockley-Read-Hall (SRH), radiative, and Auger recombination processes to the temperature and excess carrier density dependent data. The minority carrier (MC), radiative, and Auger lifetimes were observed to generally increase with increasing antimony content and decreasing layer thickness for the unintentionally doped T2SLs. The MC lifetime is limited by SRH processes at temperatures below 200 K in the unintentionally doped T2SLs. The extracted SRH defect energy levels were found to be near mid-bandgap. Also, it is observed that the MC lifetime is limited by Auger recombination in the intentionally doped T2SLs with doping levels greater than n $ 10 16 cm À3. V

Electrically Reconfigurable Metasurfaces Using Heterojunction Resonators

“…Electrons thus accumulate at high densities until they recombine with injected holes via band-to-band tunneling, Shockley-Read-Hall, [ 48 ] or Auger [ 50,51 ] processes. In the i-InSb layer, we assume an electron mobility [ 52 ] of 7000 cm 2 V −1 s −1 (400 cm 2 V −1 s −1 for holes).…”

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

“…For InAs=InðAs; SbÞ T2SLs, this strategy involves engineering the SL structure using the layer thicknesses of InAs and In(As,Sb) and the alloy composition to shift the T2SL band-edge energies in absolute energy. A previous study that focused on engineering the InAs=InðAs; SbÞ structure, while keeping a constant band gap near 5.2 μm, showed that an approximately 2k B T energy shift in the T2SL VB energy is possible, which caused the MC lifetime to increase from approximately 3 to 6 μs [9]. This result demonstrates the feasibility of modifying the SRH lifetime through band-structure engineering.…”

“…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].…”

“…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]. One significant benefit of superlattice (SL) structures is that the position of the SL valence-band-(VB) and conduction-band-(CB) edge energies and, hence, the SL band gap (E g ), on an absolute energy scale is determined by the layer thicknesses, compositions, and specific materials that make up the structure and can, therefore, be engineered.…”