Photoexcited transport in GaAs/AlAs quantum wells

We present the results of a study of the transport of optically excited carriers perpendicular to weakly coupled GaAs/AlAs multiple quantum wells imbedded in the depletion region of a p-i-n photodiode. At temperatures above 120 K the photocurrent was thermally activated. For lower temperatures the photocurrent decreased as temperature was increased. Wavelength-dependent negative differential resistance regions were present in the reverse bias region of the photoexcited current voltage (I-V) curve as a result of the Stark shifts of the lowest energy heavy hole (h1) and light hole (l1) excitons. Additional wavelength independent structure was also visible in the photoexcited I-V curves.