Bridgman growth of Hg 1−xCd xTe from melt of constant composition

Abstract

A modified Bridgman method is applied for the growth of semiconducting alloys Hg 1- x Cd x Te from the melt. The large separation between the liquidus and solidus lines in the t-x phase diagram and further non-planar melt/crystal interface shape cause significant axial and radial gradients in the composition. In order to reduce these difficulties, the proposed method - Bridgman growth from melt of constant composition (BGCC) - is based on a demand to simply ensure a melt of constant composition near the melt/crystal interface during growth. The missing CdTe is transported to the phase boundary by diffusion from a suitable source - for example floating solid CdTe. A model of diffusion of CdTe in the liquidus was verified by a fast cooling of the melt above the growing crystal and its composition analysis. In this way the equilibrium segregation coefficient and solute diffusion coefficient of CdTe were determined. As-grown crystals were p-type Hg-vacancy-doped. By an annealing near-Hg-saturated condition or in a Hg bath, and also by ion beam milling, the n-type material can be prepared. Electrical, optical and photoelectrical properties are briefly discussed.