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 elem ents 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 absorpt ion spectra in the crystals grown with different contamination levels. It has been found that the crystals grown with large hydrocarbon cont aminations always show a smooth, broad and strong absorption band over 3500-1700 cm-1. Based on the available correlation studies, it has be en argued that this band arises due to stretching vibrations of the hy droxyl and carbonyl groups which are incorporated in the form of polym erized chelate complexes in the lattice during growth. Further, it has been found that both Zn and Se substitution enhances, and hydrogen pu rging reduces, the uptake of these contaminants.