A spectroscopic study of acceptors in germanium

Zeeman and piezo-Zeeman spectroscopy have been used to study the single acceptors gallium and singly ionised zinc in germanium. While the Zeeman spectra of group III acceptors have been extensively studied by others the use, here, of high magnetic fields and high resolution have clarified the Zeeman behaviour of these, the simplest of acceptors, giving unambiguous and precise quantitative results about the ground state and the two excited states of the G and D spectral lines. These results are used to test the predictions of two theoretical treatments. The agreement between both theoretical treatments and experiment for the excited state of the D line is excellent, that for the G line is very good while there is significant disagreement between the theories themselves and with the experiment for the ground state. Similarities between the group III acceptors and singly ionised Zn are expected due to the small dependence of the higher energy states on the exact character of the impurity potential. This is suggested from comparison of the unperturbed spectra and is borne out by comparison of the Zeeman spectra. If it is assumed that the final states of the D line for Ga and singly ionised Zn in Ge are identical at the magnetic fields used here quantitative results for the ground state of singly ionised Zn are obtained. Effects such as the piezo-transverse-Zeeman effect are observed for singly ionised Zn as was the case for group III impurities, the differences being due to the different behaviours of the ground states and to the fact that singly ionised Zn in Ge has energy spacings approximately four times larger than those of the group III acceptors. Values of the phenomenological g factors have been estimated for both impurities using Zeeman measurements and these were extensively compared with g factors obtained from piezo-Zeeman results. Preliminary results are presented, without interpretation, showing the Zeeman splitting of the stress enhanced G line of singly ionised Zn in Ge.