Fabrication of MnAs microstructures on GaAs(001) substrates and their electrical properties

We explore wet and dry etching processes of thin MnAs layers grown on GaAs(0 0 1) substrates for microstructuring. Most of the common wet chemical etch solutions for GaAs react with MnAs strongly and in a peculiar manner. Unidirectional cracks are generated when the MnAs layers are thicker than 100 nm. We demonstrate that the crack generation can be avoided by choosing a suitable etch solution or etch temperature. We fabricate submicrometer-wide MnAs wires using Ar ion milling. The resistivity of the narrow channels is measured over a temperature range covering the phase transitions in MnAs between the αα, ββ, and γγ phases. The resistivity along the MnAs[0 0 0 1] direction is found to be smaller than that along the MnAs[112¯0] direction regardless of the phase. A nearly linear temperature variation of the phase fraction is deduced in the αα–ββ phase coexistence regime. The temperature coefficients of the resistivities are negative for the nonmagnetic phases.

Surface of a partly etched MnAs film grown on a GaAs(001) substrate.Figure optionsDownload full-size imageDownload as PowerPoint slide