Mismatch and thermal strain analysis in MBE-grown HgCdTe/CdZnTe

High resolution diffraction measurements of the strained lattice unit of HgCdTe and CdZnTe have been performed at temperatures varying from room temperature to 300 °C and for different lattice mismatch between substrate and layer. This investigation makes possible the determination of the coefficients of thermal expansion (CTE) and the evolution of the HgCdTe film stress during the thermal cycles. It is found that the CTE is linear with the zinc fraction for CdZnTe while it can be described by a parabolic variation as a function of the cadmium fraction for HgCdTe. The temperature evolution of the stress is found to be dictated by the CTE difference between substrate and layer up to a temperature of 150 °C above which the HgCdTe layer partially relaxes. The evolution of the stress with lattice mismatch enables the determination of the onsets for plastic relaxation for both tensile and compressive stress.

► Experimental determination of CdZnTe and HgCdTe coefficient of thermal expansion.
► Analysis of the effect of thermal strain on HgCdTe/CdZnTe layers.
► Analysis of the mismatch strain induced by zinc non-uniformity in HgCdTe/CdZnTe.
► Experimental evidence for elastic and plastic regimes for strained HgCdTe.