Experimental and theoretical piezospectroscopy of neutral copper impurity in germanium

A group-theoretical study of triple acceptors in group-IV semiconductors under an applied uniaxial force, F, has been made employing the self-consistent-field model. The ground state, constructed from three equivalent single-hole Γ8 states, is found to be itself a Γ8 state, whereas the excited states are more complex. The energy splitting of the various impurity states and the relative intensities of the associated stress-induced components have been determined for F ||,and. Only effects linear in stress have been considered. The optical absorption spectrum of the group-I impurity, neutral copper, in germanium at liquid helium temperature and above has been studied using photon energies near 40 meV and quantitative uniaxial compression with polarized radiation for F | |,,andDline.