A Study of Non‐Equilibrium Contact Potential Difference on the Surface of Photoconducting CdS Crystals

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Abstract
The contact potential difference (CPD) and field effect have been measured at room temperature on photoconductive CdS crystals with real surfaces. It is shown that the CPD is determined by the surface position of the electron quasi‐Fermi level. The surface band bending was found to be accumulative on the surface of photoconductive crystals under illumination and to be depletive on the surface of semiconductive crystals in darkness. The non‐equilibrium analogue of the well‐known thermal stabilization of the Fermi level by surface states was observed on photoconductive crystals. It was denoted as “an optical stabilization” and results from the high density of surface recombination centres.