Time-resolved electronic capture in germanium doped with hydrogen-like impurity centers

Kurzfassung

The availability of intense short-pulsed THz radiation from sources such as free electron lasers (FELs) or synchrotrons demands broad-band detectors with very short response times. This triggered a renewed interest in fast germanium (Ge) detectors. The fastest operation of Ge detectors demonstrated in the THz region of the electromagnetic spectrum so far showed an about 2-ns long decay time using highly compensated neutron transmutated p-Ge:Ga:As:Sb. The short-pulse narrow-band FEL radiation allows studying impurity photoconductivity kinetics and provides information important for optimizing the speed of response of extrinsic photoconductors. The capture of free holes and electrons in Ge doped by gallium (Ga) or antimony (Sb) has been studied by a time-resolved pump-probe experiment with the FEL FELBE at the HZDR. For Ga acceptors the relaxation times decrease with increasing pump power from approximately 3 ns to 1 ns (2 ns and 1 ns for Sb donors, respectively). The results support the development of fast photoconductive detectors in the THz region of the spectrum.