Abstract-Lifetime-limited, subnanosecond terahertz germanium photoconductive detectors

N. Deßmann¹, S. G. Pavlov², A. Pohl¹, N. V. Abrosimov³, S. Winnerl⁴, M. Mittendorff^4,5, R. Kh. Zhukavin⁶, V. V. Tsyplenkov⁶, D. V. Shengurov⁶, V. N. Shastin^6,7 and H.-W. Hübers^1,2
http://scitation.aip.org/content/aip/journal/apl/106/17/10.1063/1.4918712
1 Department of Physics, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
2 Institute of Optical Sensor Systems, German Aerospace Center (DLR), Rutherfordstr. 2, 12489 Berlin, Germany
3 Leibniz-Institute for Crystal Growth, Max-Born-Str. 2, 12489 Berlin, Germany
4 Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328 Dresden, Germany
5 Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20740, USA
6 Institute for Physics of Microstructures, Russian Academy of Sciences, GSP-105, Nizhny Novgorod, 603950, Russia
7 Nizhny Novgorod State University, 23 Prospekt Gargarina, Nizhny Novgorod 603950, Russia
Appl. Phys. Lett. 106, 171109 (2015); http://dx.doi.org/10.1063/1.4918712

The recombination times of photo-excited free charge carriers in heavily doped and highly compensated germanium are studied by a time-resolved pump-probe experiment at a frequency of ∼3 THz. The dominant dopant in the germanium samples is either antimony (n-Ge:Ga:Sb) or gallium (p-Ge:Sb:Ga) with compensating doping levels close to 100%. The recombination time of the free charge carriers measured by our pump-probe technique varies between 30 and 300 ps. It decreases with increasing pump pulse energy and increasing compensation due to high concentrations of Coulomb recombination centers. The recombination times at low pump powers are up to ten times shorter than those previously obtained for low-compensated n-Ge:Sb and p-Ge:Ga. The photoconductive detector made from this material shows the response time is in the order of its recombination time.