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High-speed photocurrent in quantum well infrared photodetectors

Hochgeschwindigkeitsphotostrom in Quantumwell Infrarot-Photodetektoren

Goodnick, S.M. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Materials and electronics for high-speed and infrared detectors
Bellingham, Wash.: SPIE, 1999 (SPIE Proceedings Series 3794)
ISBN: 0-8194-3280-6
Conference on Materials for High Speed Detectors <1999, Denver/Colo.>
Fraunhofer IAF ()
quantum well infrared photodetector; quantum well Infrarot Photodetektor; QWIP; GaAs/AlGaAs; time-resolved photocurrent; zeitaufgelöster Photostrom

Quantum well infrared photodetectors (QWIPs) are very promising for ultrafast photodetection in the 8- 12 mu m infrared regime. We report on time-resolved studies of the intersubband photocurrent in GaAs/AlGaAs (QWIPs). The photocurrent is excited by sub-picosecond infrared pulses, which are obtained by difference frequency mixing of the signal and idler waves of an optical parametric oscillator. Using a particular detector geometry with < 900 mu m (exp 2) device area, the measured electrical pulses have a full-width at half-maximum of only 16 ps and a 10-90 per cent rise time of 13 ps. For practical applications, in particular for heterodyne detection, it is desirable to reduce the noise floor by using a cooled low-noise preamplifier. We have performed experiments with a low-temperature hybrid circuit consisting of a QWIP in connection with a GaAs transimpedance amplifier based on HEMT technology. This configuration yields a rise time of 19 ps at an amplifier gain of approximately 35 dB.