Ultrafast Carrier Drift and Field Screening in a Biased GaAs/AlGaAs QuantumWell Infrared Photodetector

摘要

We present time and spectral resolved pump and probe studies of theintersubband dynamics in a bound to quasi-bound GaAs/AlGaAs quantum wellinfrared photodetector (QWIP) dependent on the external electric field. With appliedelectrical field 35%-45% of the excited electrons escape to continuum states and areaccelerated along the electrical field. Within time constants between 5 ps and 9 psthese electrons are recaptured by wells in the low field bulk domain. The redistributionof the carriers in the picosecond time regime and the screening of the external fielddue to the separation between electrons and donors lead to a change of the absorptionspectrum for a time period shorter than the intrinsic response time of the electricalcircuit.