High detectivity PbSxSe1-x films for mid-wavelength infrared detectors

•Microstructure of lead chalcogenide films depends on the growth temperature.•High-temperature PbSe0.6S0.4 is columnar with [111] texture.•Low-temperature PbSe0.6S0.4 does not demonstrate texture.•Photoresponse of PbSe0.6S0.4 improves with the decrease of the growth temperature. Lead salt detectors consisting of PbSe-PbS alloys offer detection capability in the 3-5 µm midinfrared wavelength range and exhibit responsivity at near-room temperature conditions. In this paper, we present the growth of PbSe0.6S0.4 layers by physical vapor deposition and evaluate their properties and performance as a function of the deposition temperatures (50°C and 200°C). Specifically, the influences of deposition temperature on the microstructure of PbSe0.6S0.4 and its subsequent detectivity is evaluated. The high temperature growth at 200°C results in films with the near-columnar fiber-like microstructure; low temperature growth at 50°C results in films with the fine equiaxed grains. Importantly, reduction of the growth temperature leads to a better photoresponse (up to two orders of magnitude) following the O2 sensitization of the PbSe0.6S0.4 films. We attribute this improvement to the more effective oxidation process due to a large increase in the density of the grain boundaries as a result of a smaller grain size.