Effect of Thin Space-Charge Layers on Exciton Reflectance

Abstract

Resonance reflectance in semiconductors in the frequency region of exciton transitions depends strongly on characteristics of the near-surface space-charge layers. It is shown by numerical computation that the majority of the exciton reflection lineshapes observed on CdS earlier may be explained by the presence of a thin (10 to 100 nm) space-charge layer with a relatively high (104 to 105 V/cm) surface electric field. Various treatments of surfaces alter charges on and below them thus modifying the electric field distribution. The latter causes changes in the exciton reflectance. Transformations of the exciton lineshapes under the action of illumination and electron bombardment are discussed in detail for the case of CdS. The lineshapes show drastic variations with expositions of both influences. In a single experiment one may observe all of the anomalies typical for the thin space-charge layers. [Russian Text Ignored].