Electronic transport properties of GeS single crystals grown by vapor transport from molten GeS source

Abstract

The electrical properties of GeS single-crystal are determined by the Van der Pauw method as a function of the temperature, thus establishing for the first time the dependence of electrical resistivity on both carrier concentration and mobility. This was possible after the repeated growth of GeS by vapor transport from molten GeS so that high-purity (low concentration of Fe and Na impurities) and high-crystalline (XRC FWHM = 2 min.) GeS single-crystals could be obtained. An extraordinary high electrical conductivity is observed between 180 and 450 K, ranging from 1.1 x10-2 to 3.7 x10-5 Ω−1 cm−1. Acceptors are activated over the whole temperature range, while donor activation takes place above 280 K, partially compensating the hole carrier concentration. In contrast, the mobility is proportional to T−2.4 over the whole temperature range, indicating the predominance of lattice scattering. At room temperature the electrical conductivity is as high as 6.7 × 10-3 Ω−1 cm−1, originating from a hole concentration of 1.7 × 1015 cm−3 and mobility of 25 cm2/Vs.