11 June 2013 Time-resolved photoluminescence study of carrier recombination and transport in type-II superlattice infrared detector materials
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Time-resolved photoluminescence (TRPL) is used to study the minority carrier lifetime in type-II superlattice (T2SL) infrared detector materials to investigate the recombination mechanisms, trap states and transport properties that currently limit their performance. Measurements of carrier lifetime have shown that InAs/Ga1-xInxSb T2SLs are dominated by non-radiative Shockley-Read-Hall (SRH) recombination, resulting in short minority carrier lifetimes (10’s of nanoseconds at 77 K). A trap energy of ~60 meV above the valence band is identified in mid-wavelength infrared n-type InAs/Ga1-xInxSb T2SLs, where trap saturation (non-exponential decay) is observed under high injection levels due to a significantly faster hole capture rate than electron capture rate. Lifetime measurements in “Ga-free” InAs/InAs1-xSbx T2SLs exhibit an order-of-magnitude increase in lifetime (100’s of nanoseconds at 77 K) with contributions from both radiative and non-radiative recombination. This improvement is attributed to the reduction of non-radiative recombination centers from the superlattice with the elimination of Ga and suggests that the SRH trap(s) limiting the carrier lifetime of InAs/Ga1-xInxSb T2SLs is native to the Ga1-xInxSb layer. Additionally, radiative recombination is observed in an InAs/GaSb T2SL using a sub-bandgap CW laser to saturate the SRH recombination centers, yielding a radiative lifetime of ~140 ns at 77 K. Since carrier transport is a concern in Ga-free T2SLs, it is investigated by studying samples grown with and without barriers (to contain injected carriers to the absorber region). It is determined that carrier transport is poor in InAs/InAs1-xSbx T2SLs because negligible differences are observed in the carrier lifetime.
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Blair C. Connelly, Blair C. Connelly, Grace D. Metcalfe, Grace D. Metcalfe, Hongen Shen, Hongen Shen, Michael Wraback, Michael Wraback, "Time-resolved photoluminescence study of carrier recombination and transport in type-II superlattice infrared detector materials", Proc. SPIE 8704, Infrared Technology and Applications XXXIX, 87040V (11 June 2013); doi: 10.1117/12.2016202; https://doi.org/10.1117/12.2016202

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