A study on contaminations during bulk growth of CdTe crystals

In this paper we present an analysis of certain unintentional dopants that arise due to spurious surface oxides on starting high purity elements and residual gases (including hydrocarbons) in the sealed quartz containers during bulk growth of CdTe crystals. The analysis is based on comparing, assigning and interpreting the observed infrared absorption spectra in the crystals grown with different contamination levels. It has been found that the crystals grown with large hydrocarbon contaminations always show a smooth, broad and strong absorption band over 1700–3500 cm-1. Based on the available correlation studies, it has been argued that this band arises due to stretching vibrations of the hydroxyl and carbonyl groups which are incorporated in the form of polymerized chelate complexes in the lattice during growth. Further, it has been found that both Zn and Se substitution enhances, and hydrogen purging reduces, the uptake of these contaminants.