Influence of the shape of a quasi-one-dimensional channel on the quantized acousto-electric current

Quantized currents induced by surface acoustic waves in a submicron channel offer a possible way towards a current standard. Its precision is expected to depend strongly on the shape of the static potential. In order to investigate this crucial dependence we have fabricated samples where the channel is comprised of three smaller split-gates with the possibility to electrically tune the channel geometry. We show that the channel exit has practically no influence on the quantization, in agreement with a simple electrostatic model. The entrance of the channel, however, determines the RF-power level required to produce quantized currents.