Electron spin resonance of doped glow‐discharge amorphous germanium

ESR‐spectra and transport properties of a‐Ge:H, prepared by decomposition of GeH 4 in a glow‐discharge, are investigated for different phosphorus and boron doping. Undoped and moderately doped samples show the usual resonance at g = 2.0225 due to dangling bonds. For high doping levels, however, two new lines are found: high boron doping leads to a resonance at g = 2.0535 with a linewidth of 112 G, high phosphorus doping to a line at g = 2.0120 with Δ H pp = 33 G. These lines are attributed to localized holes and electrons in the tails of valence and conduction band, respectively. The linewidth of all resonances is the combination of a g ‐spectrum Δ H pp ( g ) and a considerably smaller residual linewidth Δ H pp ( r ) caused by unresolved hyperfine interaction. A simple relation between the g ‐shift g–g 0 and Δ H pp ( g ) is found which explains the similar doping dependence of g ‐value and linewidth. From the dependence of the spin density N s on the conductivity activation energy E σ a model for the density of states in the mobility gap is deduced. A comparison between the ESR‐data of a‐Ge: H and a‐Si: H shows that g ‐shifts and linewidths of the three resonances are for a‐Ge: H by a factor of about six larger than for the corresponding lines of a‐Si: H.