Acoustoelectric measurements of minority and majority carrier mobilities in semiconductors including Hg1−x Cd x Te

Acoustoelectric voltages versus absorbed surface acoustic wave (SAW) power measurements are used to nondestructively determine carrier mobilities in bulk silicon, GaAs and epitaxial Hg_1−x Cd _x Te employing a separate medium convolver structure. The longitudinal component of the acoustoelectric signals (LAV) has been used in the past to determine the carrier mobilities in semiconductor films. In the present work, it is shown that the transverse component of the acoustoelectric signals (TAV) can also be used to measure the carrier mobilities. TAV and LAV measurements yield mobilities in perpendicular directions. Hence, these measurements can be used to study the electron mobilities of a two-dimensional electron system in superlattices. A new delay line structure is introduced to invert the semiconductor surface through the field effect to measure the minority carrier mobilities. Carrier mobilities in graded epitaxial Hg_1−x Cd _x Te are measured after subsequent etching of the surface to obtain the mobility values versus depth. The findings of the above measurements and Hall measurements are in satisfactory agreement. Partially supported by Night Vision Lab, through Contract No. DAAG 29-81-D-0100