Carrier dynamics in doped Ge measured at the free electron laser facility FELBE

Abstract

Cooled germanium (Ge) photoconductive detectors are one of the most sensitive detectors at terahertz (THz) frequencies. They are widely used in laboratory spectroscopy and imaging experiments. The speed of a Ge photoconductive detector is set by technical limitations such as the bias circuit, the geometry of the detector crystal and the electric field applied to the .detector. The recovery speed of the detector material is, however, fundamentally limited only by the lifetimes of the intraband relaxation of the free charge carriers within the valence or conduction band and by band-to-impurity relaxation (capture) down to the impurity ground state. Therefore, capture and intraband relaxation processes have been measured for different dopants in uncompensated and compensated n- and p-type Ge by a pump-probe technique at the free electron laser facility FELBE.