Electrical and Photoelectric Properties of Modified Chalcogenide Vitreous Semiconductors

Abstract

For a long time after the discovery of chalcogenide vitreous semi-conductors (ChVS) [1,2], it was believed that, unlike crystalline semiconductors, ChVS are practically insensitive to doping with various impurities, i.e., that extrinsic conductivity does not appear [3–5]. Such a pronounced difference between crystalline and vitreous semiconductors was bound to draw the attention of prominent physicists. One of the first who was interested in this problem was Professor N.F. Mott. This led to a number of papers on the insensitivity of ChVS to doping [6,7]. This idea persisted up to the middle 70’s when the first papers on the influence of Ag on the electrical and optical properties of As₂Se₃ appeared [8]. At the Seventh International Conference on Liquid and Amorphous Semiconductors in 1977, S.R. Ovshinsky reported on the possibility of controlling the electrical properties of ChVS by introducing considerable amounts of impurities into his complex composition ChVS using, for example, RF cosputtering technique. The considerable amounts of impurities introduced and the absence of crystallization determined the name of the new method as modification method [9,10]. Later the method was tested on a number of other ChVS including the well-known chalcogenide glasses AS₂S₃ and As₂Se₃ [11–16]. The main results of influencing the electrical and photoelectric properties of As₂Se₃ by the modification method will be described below.