Barrier thickness dependence of photocurrent spectral intensity in GaAs/AlAs superlattice p-i-n diodes

Abstract

We have experimentally studied photocurrent (PC) spectral intensity in GaAs/AlAs superlattices (SL) with different barrier thickness [LB=2∼18 monolayers (ML)]. When the LB value is less than 6 ML, the PC spectra reveal clear evidence for the Wannier–Stark localization and the PC intensity shows an initially steep increase with the field (at less than 30 kV/cm) over a wide spectral range and then saturates at nearly the same level regardless of LB. For thick LB samples, however, the PC intensity is strongly dependent on the LB value, very gradually increases and reaches the saturation level under extremely high field conditions. These results are rigorously explained by considering the photogenerated carriers tunneling and the competition between the recombination lifetime and the tunneling escape time which is strongly varied by changing the barrier thickness.