Optical Absorption and Photoconductivity in Magnesium Oxide Crystals

Abstract

Optical absorption and photoconductivity spectra of magnesium oxide crystals from various sources are presented. The effects of ultraviolet and x-ray irradiation are described, and the results are interpreted in terms of valence changes of impurities, principally iron. A method for the analysis of the photoconductivity data is given. This method corrects for the effects of strong nonionizing absorption, which may lead to spurious peaks in photoconductivity spectra. The sign of the optically excited charge carriers was deduced by a method which involves the formation of a space-charge field by the motion of carriers in an applied electric field, and the detection of the asymmetry in this space-charge field when carriers are subsequently allowed to move under the influence of the space-charge field only.