Energy, Orientation, and Temperature Dependence of Defect Formation in Electron Irradiation of n-Type Germanium

Publisher Website
Google Scholar
Abstract
From measurements of change in conductivity with electron irradiation of thin n‐type germanium samples at 79°K, a threshold energy for the formation of stable acceptor centers has been determined. It is found to be 355±5 kev, corresponding to 15.1 ev for the lightest mass germanium isotope at rest. Taking into account the contribution of lattice vibrations to the displacement energy the threshold is ∼16 ev. An orientation dependence has been found in the rate of formation of the centers in agreement with the predictions of Kohn. In order of decreasing rate of center formation the three orientations examined are (111), (110), (100). There is no corresponding orientation dependence in the threshold energy itself. The energy dependence of the rate of acceptor formation suggests the defects are not the closest vacancy‐interstitial pairs. A positive temperature dependence of the rate of acceptor formation has been found. This effect is largest at lowest electron energies. It is not explicable by lattice vibrations, although they can contribute to the effect between 79°K and room temperature. The apparent threshold changes by ∼100 kev between 21 and 263°K.