Effect of process changes on the properties of Cd xHg 1−xTe crystals grown by Bridgman using ACRT

Abstract

Changes to the basic accelerated crucible rotation technique (ACRT) as applied to the growth of Cd x Hg 1− x Te (CMT) have been effected and the resultant crystal properties determined. Faster stable growth rates are found to be possible with ACRT. The use of flat-based growth ampoules leads to improved macrocrystallinity and radial compositional uniformity in the early stages of growth. Predictions made from quenching experiments on the effect of maximum rotation rate have been confirmed. Addition of convective mixing to that produced by ACRT gives rise to a deterioration in crystal properties. Changes in starting composition together with changes to the maximum rotation rate enables a degree of “tuning” of the process, in terms of x, to be achieved. It appears that an optimum amount of melt mixing can be set up which results in large amounts of material with the desired composition and relatively free from grain boundaries, which are known to have adverse effects on devices. Larger diameter crystals have also been produced with good radial compositional uniformity.