Correlation between cadmium telluride surface oxidation and metal junctions

X-ray photoelectron spectroscopy analysis of cleaved single crystal CdTe {110} surfaces exposed to air indicates the growth of tellurium dioxide (TeO2). Its presence is directly reflected in the properties of Cr/CdTe junctions formed on the cleaved surfaces exposed to air for different lengths of time; the saturation current for a junction formed on a cleaved surface exposed to air for 5 min is 2×10−8 A/cm2, whereas a surface exposed to air for 2 h yields a junction with a saturation current of 4×10−9 A/cm2. Corresponding values of open circuit voltages are 0.45 and 0.55 V, respectively. The increase in the open circuit voltage is directly attributable to the presence of TeO2 on the air exposed surface.