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Responsivity and Gain of InGaAs/GaAs-QWIPs and GaAs/AlGaAs-QWIPS: a Comparative Study

Responsivität und Gewinn von InGaAs/GaAs-QWIPs und GaAs/AlGaAs-QWIPS: eine vergleichende Studie
: Rehm, R.; Schneider, H.; Schwarz, K.; Walther, M.; Koidl, P.; Weimann, G.


Brown, G.J. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Photodetectors: Materials and Devices VI : 22 - 24 January 2001, San Jose
Bellingham/Wash.: SPIE, 2001 (SPIE Proceedings Series 4288)
ISBN: 0-8194-3966-5
Conference Photodetectors <6, 2001, San Jose/Calif.>
Photonics West <2001, San Jose/Calif.>
Conference Paper
Fraunhofer IAF ()
infrared detector; Infrarotdetektor; Quantum well; Quantentopf; QWIP; InGaAs; responsitivity; Responsivität; gain; Gewinn

We experimentally compare the peak responsivity R, gain g, quantum efficiency, and detectivity of GaAs/AlGaAs-QWIPs with devices based on the competing material system InGaAs/GaAs. For this purpose we use a typical n-type GaAs/AlGaAs-QWIP and three n-type InGaAs/GaAs-QWIPs with varying doping densities. R and g of the GaAs/AlGaAs-QWIP show a typical negative differential behavior, while both quantities grow monotonously with increasing bias voltage in the case of the InGaAs/GaAs-QWIPs. For identical nominal doping densities and similar cutoff wavelengths between 8.9 micrometers and 9 micrometers , InGaAs/GaAs-QWIPs show much higher responsivities than GaAs/AlGaAs-QWIPs. The ratio between these responsivities is 2.5 at the bias voltage where the GaAs/AlGaAs-QWIP has its maximum. By making use of the different bias dependence of the responsivity in both types of QWIPs a further enhancement of this factor is achieved. Nevertheless, both types of QWIPs show comparable detectivities. This is due to the fact that the gain has a negligible influence on the detectivity. In conclusion, InGaAs/GaAs-QWIPs are promising if high responsivities and short integration times are required.