SPACE, TIME AND FUNDAMENTAL INTERACTIONS

INFLUENCE OF ELECTRON BOMBARDMENT TO THE PHOTO-CONDUCTIVITY SPECTRA OF CDS CRYSTALS

Batyrev A.S., Bisengaliev R.A., Sumyanova E.V.

The paper presents the results of studies of the effect of electron bombardment on the spectral distribution of the photoconductivity of CdS single crystals in the region of the fundamental absorption edge at liquid nitrogen temperature ( T = 77 K). It is shown that the photosensitivity of the crystal, as well as the fine (exciton) structure of the photoconductivity spectra, which is formed in a thin surface layer of a semiconductor, changes under the influence of the bombardment of the sample by low-energy electrons. Experiments have shown that electron bombardment-induced transformation of the photoconductivity spectra of CdS crystals is associated with stimulated electron bombardment by desorption of oxygen from the surface of the sample, which creates a negative surface charge. It is shown that the effect of electron bombardment on the spectra of a low-temperature photoconductivity of crystals of the 1st and 2nd groups of the fine structure has a different character. Such a difference is associated with a different composition of the surface layer of semiconductors. The CdS crystals of the 1st group are characterized by the presence of excess interstitial cadmium atoms in the surface layer. These atoms play the role of shallow donors and create enriching zones at some distance from the semiconductor surface. Near the surface of such crystals, there exists a depleting bend of energy bands caused by oxygen adsorbed on the surface and forming a potential well for holes.