Effect of substrate dislocations on the Hg in-diffusion in CdZnTe substrates used for HgCdTe epilayer growth

Chemical-etched HgCdTe epilayers grown onto CdZnTe substrates have been studied using defect etching and EDS on cleaved (1 1 0) face. Formation of etch pits and mercury (Hg) in-diffusion into CZT substrate has been correlated with the substrate quality i.e. the presence of dislocations around second phase inclusions. That the Hg in-diffusion takes place through these dislocations is authenticated by the presence of Te-inclusions in substrates where large density of etch pits are revealed after chemical etching. X-ray rocking curve measurements were carried out to reveal crystalline quality of the substrates. FTIR spectroscopy indicates low transmission values and absence of interference fringes in MCT epilayers with large Hg diffusion. Hg diffusion into CZT substrate upto 25 μm in samples with low FWHM values and upto 250 μm in samples with multiple peaks and high FWHM values was observed.