Scanned gate microscopy of surface-acoustic-wave-induced current through a depleted one-dimensional GaAs channel

摘要

We present scanned gate microscopy images of the surface-acoustic-wave (SAW)-induced current through a depleted GaAs one-dimensional channel. The images show a crescent-shaped feature, which splits into two fragments when the tip bias is taken more negative. This is consistent with depopulation of the SAW minima when the electron energy is out of equilibrium with the source two-dimensional electron system, where the maximum longitudinal potential gradient, along the length of the channel, sets a limit on the SAW-induced current. Part of a circular feature located near die channel exit is seen in the same images, which is probably caused by a low-amplitude reflected SAW with transport induced by a turnstile mechanism. Image analysis provides several parameters that are related to the electrostatic landscape at the channel entrance and are critical for controlling electron capture by the SAW potential. The parameters are the maximum potential gradient, the length of the channel entrance, and the precise location of the maximum potential gradient.