Electrical detection of ambipolar acoustic carrier transport by surface acoustic waves

We have investigated the efficiency of the ambipolar transport of photogenerated electrons and holes in (Al,Ga)As structures by surface acoustic waves (SAWs). In the experiments, the photogenerated electrons and holes transported by the SAW are collected by a lateral p-^i-n junction and detected by electrometers. Carrier recombination during transport was also studied by detecting the photoluminescence emitted along the SAW path by the transported carriers. We show that the acoustic transport efficiency improves by using biased metallic guides along the SAW beam to create independent transport channels for electrons and holes. By optimizing the photon absorption efficiency and the amplitude of the acoustic fields, we demonstrated overall transport efficiencies above 85% for transport lengths on the order of 300 μm.