Spectroscopic Study of the Symmetries and Deformation-Potential Constants of Singly Ionized Zinc in Germanium. Theory

This paper presents a theoretical study of the relative intensities and energy splittings of the excitation lines of a single-hole acceptor in a group-IV semiconductor. Group theoretical methods are used to obtain the selection rules for electric dipole transitions and to give the relative intensities of the stress-induced components of a given absorption line. This study became necessary in the course of our piezospectroscopic investigation of the excitation spectrum of singly ionized zinc in germanium because previous such studies lacked sufficient generality. The diagramatic representation of the results of our calculations are specifically suited to the above acceptor impurity. The theory reveals that the ratios of the intensities of the components of a ${\Gamma }_8\to {\Gamma }_8$ transition depend upon two real parameters instead of one, as was previously believed. One of these parameters may be determined unambiguously from a measurement with uniaxial compression along a $〈111〉$ direction. The magnitude of the other may be found from measurements with compression parallel to $〈100〉$ and $〈110〉$. At the same time symmetry assignments can be made to the stress-induced acceptor sublevels by comparison of the observed and theoretical relative intensities.