Characterization of epitaxial cadmium telluride and lead telluride layers grown by R.F. magnetron sputtering.

Abstract

Sputter-deposited heteroepitaxial layers of (100) CdTe $\Vert$ (100) KBr prepared at growth temperatures of 300-325$\sp\circ$C are found to be p-type with high dark resistivities on the order of 2 $\times$ 10$\sp5$ ohm-cm. The epilayers are highly photoconducting. The photoconductivity $\sigma\sb{ph}$ (expressed as $\sigma\sb{ph} \propto f\sp{\gamma}$) is observed to exhibit a sublinear ($\gamma$ $\prec$ 1) dependence on illumination intensity f. Photo-Hall effect measurements show that the photoconductivity is due to change in carrier concentration and not due to any enhancement in the carrier mobility. Moreover, the photocurrent is carried by holes. Hall measurements on sputter-deposited epitaxial PbTe films have confirmed that samples prepared at high growth temperatures are n-type and those grown at low substrate temperatures are p-type, irrespective of the substrate bias applied during growth. The low temperature mobility values in the sputter-deposited samples are found to be limited by a temperature-independent neutral impurity scattering mechanism. One of the features of heteroepitaxial growth is the existence of a large density of structural defects at the interface due to lattice mismatch. (Abstract shortened by UMI.)