Surface excitons with a hole localized in a quantum inversion layer

The observation of a new type of structure in the photocurrent spectrum of CdS crystals at 4.2 K is reported. The spectral position and intensity of this structure are extremely sensitive to the parameters of the space-charge layer, controlled by an intense illumination of the crystals in the region of 510 nm and below. The structure is attributed to the excitation of quasi-2d surface excitons with a hole localized in a quantum inversion layer. The structure is not seen in the reflection, and its presence in the photocurrent spectrum is attributed to the greater sensitivity of this method.