Is Hg1 − xCdxTe grown epitaxially by the travelling heater method? Does it matter?

Abstract Crystal growth by the travelling heater method (THM) is considered to be a large scale, continuous, liquid phase epitaxial (LPE) process [e.g. R. Triboulet et al. J. Crystal Growth 79 (1986) 695]. We studied the structural perfection of Hg 1 − x Cd x Te crystals grown by THM using preferential chemical etching and X-ray double crystal rocking curves. In principle, THM is similar to LPE; in practice, the Hg 1 − x Cd x Te crystals are not epitaxially grown. The high temperature gradients involved in the THM growth process cause a stress field. This stress creates dislocations, which pile up by polygonization to form a veining pattern of low angle sub-grain boundaries (LASGBs) in the crystal. Such crystals, consisting of a mosaic of small, almost perfectly aligned single crystals, may only be considered “oriented grown”. The LASGBs have a major detrimental effect on the performance of photodiode arrays for the detection of infrared radiation. Diode leakage depends on the etch-pit density along the LASGB, the proximity of the diode and the extent of intersection of the diode by the LASGBs.