Interpretation of acceptor excitation spectra in uniaxially stressed germanium

The irreducible-spherical-tensor method of Baldereschi and Lipari is extended to include the effect of uniaxial stress on the energy levels of effective-mass acceptors in cubic semiconductors. The Hamiltonians with uniaxial stress along 〈001〉 and 〈111〉 are developed explicitly. The method is then applied to acceptors in germanium. The binding energies of the ground state and the first 18 odd-parity excited states with uniaxial stress along each of both directions are computed for stress intensities ranging from ${10}^6$ to ${10}^9$ Pa. This covers the low-, intermediate-, and high-stress regions. The results are compared to the available experimental data from far-infrared piezospectroscopy, and the calculation is found to be very accurate up to the high-stress limit.