TEMPERATURE-DEPENDENT COMPENSATION AND OPTICAL QUENCHING BY THERMAL OXYGEN DONORS IN GERMANIUM

Photothermal ionization spectroscopy of germanium, doped in the impuri ty-band conduction range with gallium acceptors and with thermal oxyge n donors, reveals that the donors and acceptors compensate each other at temperatures higher than about 5 K, but that the impurities coexist as neutral donors and acceptors at lower temperatures. At the lowest temperatures, optical quenching is observed for wavelengths where both impurities have transitions. These effects are used to infer a weak c oupling between the neutral acceptor and donor states. The small stren gth of this coupling sets the thermal oxygen donor apart from all othe r shallow donors in germanium and silicon.