Large-Strain Dependence of the Acceptor Binding Energy in Germanium

Abstract

The strain dependence of the activation energy in $p$-Ge subject to large (∼0.5%) uniaxial compressional strains has been studied for two different Group III acceptors. For both [100] and [111] compression the energy surfaces have been found to be oblate, that is, $m_{\perp }>m_{\mathrm{II}}$. From Price's theory of the binding-energy strain dependence, the applicable deformation potential elements are found to be $b=-2.1\mathrm{}$ eV and $d=-7.0\mathrm{}$ eV. Unexpectedly orientation-dependent "chemical shift" effects have been found for both Al and In impurities; the deviation of the binding energy extrapolated to infinite strain from that calculated in the effective-mass approximation is found to be ∼4 times as great for [111] strain as for [100] strain. The experimental technique is briefly described.