Mn-impurity-induced simple pair defect states in Bi-modified amorphous semiconductors Ge₂₀S_79·5-xBi_xMn_0·5

Abstract

Measurements of the a.c. conductivity of Bi-modified Mn-doped semiconducting glasses Ge₂₀S_79·5-x,Bi_xMn_0·5, have been carried out in the frequency range 100Hz-10kHz and at temperatures from 180 to 445 K for the first time. The a.c. conductivity of samples doped with Mn does not follow the well known relation σ_a.c = Aω^S A pronounced peak in the temperature dependence of the a.c. conductivity is found. The experimental results are interpreted in terms of a simple pair model. The analysis reveals that Mn impurities induce defect states deep in the band gap which form simple pairs with the same intersite separation for all pairs.