Acoustic charge transport in an (Al,Ga)As/GaAs heterojunction structure grown by molecular‐beam epitaxy

The demonstration of charge transport in GaAs epitaxial layers by surface acoustic waves in 1982 has led to a great deal of interest in using acoustic charge transport (ACT) technology for high‐speed analog signal processors. Successful implementation of ACT effects requires confining the moving charge packets to a buried layer. This was originally accomplished by biasing a thick, lightly doped n‐GaAs layer (about 4 μm low‐1015/cm3) with electrodes at the epilayer surface and at the back of the semi‐insulating substrate, leading to problems in device fabrication and reproducibility, as well as making monolithic integration with field effect transistors (FET’s) difficult. The logical solution to these problems seemed to be using the charge confining capability inherent in heterojunctions. We report here the first observation of acoustic charge transport in a heterojunction structure. The heterojunction acoustic charge transport (HACT) epitaxial structures were grown by molecular‐beam epitaxy and are compri...