Quantum oscillations in the photocurrent of GaAs/AlAs<i>p-i-n</i>diodes

Abstract

We report large amplitude quantum oscillations and negative differential conductance in the bias voltage-dependent photocurrent of p-i-n GaAs diodes with an AlAs barrier in the intrinsic ($i$) region. The oscillations appear only when the devices are illuminated with above-band gap radiation. They are strongly suppressed by a weak (\ensuremath{\sim}2 T) in-plane magnetic field. Their period, amplitude, and magnetic field dependence are explained in terms of the quantized motion of confined photoexcited electrons and holes in the triangular potential wells formed by the AlAs barrier and the strong electric field in the intrinsic region. With increasing electric field, the energy levels of the electrons (holes) successively reach the top of their confining potentials, thus leading to a larger overlap of their wave functions with the free carriers in the $p$- (and $n$-) doped electrodes and to the observed oscillatory modulation of the recombination rate and photocurrent as a function of the applied voltage. The effect on the photocurrent oscillations amplitude of placing a layer of InAs quantum dots in the AlAs barrier layer is also examined.