Transition from Electron Transport to Ambipolar Transport in Photoexcited GaAs/AlAs Superlattices

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Abstract
We report dynamical properties of both electron transport and ambipolar transport perpendicular to the GaAs/AlAs superlattice structures using a time-resolved luminescence spectroscopy at 77 K. Changing photoexcited carrier densities, we found both types of the transport and thus estimated both mobilities in miniband states of the superlattices (L B=0.90 nm and L z=3.18 nm) with an enlarged well (L z=6.36 nm). When the carrier density is lower than the residual acceptor density N A-N D, the electron transport is observed. At higher excitation density exceeding N A-N D, the ambipolar transport appears, showing a lower mobility of holes.