Electron spin resonance of doped glow‐discharge amorphous germanium

ESR‐spectra and transport properties of a‐Ge:H, prepared by decomposition of GeH4 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 ΔHpp = 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 ΔHpp(g) and a considerably smaller residual linewidth ΔHpp(r) caused by unresolved hyperfine interaction. A simple relation between the g‐shift g–g0 and ΔHpp(g) is found which explains the similar doping dependence of g‐value and linewidth. From the dependence of the spin density Ns on the conductivity activation energy Eσ 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.