Perpendicular transport of photoexcited carriers influenced by heterointerface disorder in GaAs/AlAs superlattices

Perpendicular tunneling transport of photoexcited carriers sinking into an intentionally enlarged GaAs single quantum well (SQW) in GaAs/AlAs short-period superlattices (SPS) is investigated as a function of lattice temperature (T) by steady-state and time-resolved photoluminescence (TR-PL) experiments. By measuring PL signals from SPS as well as from SQW to monitor the transport efficiency, it is found that, while a weak ambipolar tunneling-assisted hopping conduction prevails at lower T via localized states formed due to heterointerface disorder within the SPS layer, the Bloch-type transport is observed due to thermal activation of photoexcited carriers to the extended miniband states at T>30 K. This temperature evolution of the perpendicular transport is directly evidence by TR-PL measurements and rigorously explained by a rate equation analysis.