Growth and Electrical Properties of Zinc-Cadmium Sulfide Graded-Band-Gap Crystals

Abstract

Large quasi‐single crystals of Zn_xCd_1−xS with increasing x along the growth direction, have been successfully grown by vapor‐growth techniques. Typical dimensions are 15×3×4 mm. The growth mechanism is studied and, as a result, it is believed that the thermal conductivity plays a decisive role. Position‐dependent optical and electrical studies on these crystals have revealed that the crystals with a slowly varying composition can be described by a graded band gap while the properties of crystals having a more abrupt change in composition are determined by lattice defects. Most of the crystals exhibit photoluminescence and high‐field electroluminescence at low temperatures. From the optical and electrical data an energy‐band diagram for graded Zn_xCd_1−xS is deduced with the position‐dependent band gap accounted for by the position‐dependent electron affinity.