IV-VI on Fluoride/Si Structures for IR-Sensor Array Applications

Abstract

AbstractEpitaxial narrow gap IV-VI layers on Si-substrates offer an alternate to Hg1−xCdxTe for IR-focal plane arrays with similar ultimate sensitivities. We report on the following improvements in reaching the goal of an easily producible fully monolithic IV-VI-on-active-Si IRFPA: (1) Up to now, compatibility with the Si-substrate was reached through use of a stacked CaF2/BaF2 buffer layer. This layer is replaced by a very thin CaF2 buffer only, which is more suitable for photolithographic processing. (2) Fine resolution wet etching of the IV-VI layers is much easier and reproducible with this new type of buffer. (3) Good homogeneity of cut-off wavelengths is obtained: For a 12 mm long linear Pb1−xSnxSe array with 10.2 μm cut-off wavelength at 95K, the variation in cut-off is smaller than 0.1 μm. (4) The thermal mismatch strain relaxes by dislocation glide even at cryogenic temperatures and after many thermal cycles.