Spectroscopy of the hole population in bound excited acceptor states during recombination in p-type Ge

Abstract

We have designed a new type of far-infrared (FIR) pump-and-probe experiment to investigate the hole population in bound excited states of hydrogenic acceptors in germanium during hole capture. In our experiment holes are pumped from the acceptor ground state to the valence band by a blackbody emitter. The bound excited states of the acceptor are probed for captured holes by FIR-laser radiation with photon energies large enough to re-excite holes to the valence band. The re-excited holes are detected by measuring the FIR-laser induced photoconductive response of the Ge samples. We have been able to prove for the first time in a direct measurement that a fraction of the recombining holes are indeed captured into excited bound acceptor states.