Analysis of the traveling-wave technique for measuring mobilities in low-conductivity semiconductors

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Abstract
The traveling-wave method of Adler, Datta, Janes, and Hunsinger for determining the drift mobility and the sign of the majority carriers in low-mobility semiconductors is analyzed. It is found that in homogeneous semiconducting films the acoustoelectric voltage originates from two surface currents which in turn are a consequence of the boundary conditions at the film surfaces. The acoustoelectric effect vanishes in the bulk when diffusion of carriers is negligible in the transport equation. The effect of band bending and surface inversion layers on the acoustoelectric voltage is discussed qualitatively. The drift mobility measured by the traveling-wave technique is interpreted in terms of the multiple-trapping model commonly used for amorphous semiconductors.