Bright mid-infrared photoluminescence from high dislocation density\n epitaxial PbSe films on GaAs

Abstract

We report on photoluminescence in the 3-7 $\\mu$m mid-wave infrared (MWIR)\nrange from sub-100 nm strained thin films of rocksalt PbSe(001) grown on\nGaAs(001) substrates by molecular beam epitaxy. These bare films, grown\nepitaxially at temperatures below 400 {\\deg}C, luminesce brightly at room\ntemperature and have minority carrier lifetimes as long as 172 ns. The\nrelatively long lifetimes in PbSe thin films are achievable despite threading\ndislocation densities exceeding $10^9$ $cm^{-2}$ arising from island growth on\nthe nearly 8% lattice- and crystal-structure-mismatched GaAs substrate. Using\nquasi-continuous-wave and time-resolved photoluminescence, we show\nShockley-Read-Hall recombination is slow in our high dislocation density PbSe\nfilms at room temperature, a hallmark of defect tolerance. Power-dependent\nphotoluminescence and high injection excess carrier lifetimes at room\ntemperature suggest that degenerate Auger recombination limits the efficiency\nof our films, though the Auger recombination rates are significantly lower than\nequivalent, III-V bulk materials and even a bit slower than expectations for\nbulk PbSe. Consequently, the combined effects of defect tolerance and low Auger\nrecombination rates yield an estimated peak internal quantum efficiency of\nroughly 30% at room temperature, unparalleled in the MWIR for a severely\nlattice-mismatched thin film. We anticipate substantial opportunities for\nimproving performance by optimizing crystal growth as well as understanding\nAuger processes in thin films. These results highlight the unique opportunity\nto harness the unusual chemical bonding in PbSe and related IV-VI\nsemiconductors for heterogeneously integrated mid-infrared light sources\nconstrained by tight thermal budgets in new device designs.\n