Variations in composition in binary and ternary semiconductors utilizing electrolyte electroreflectance: A topographical investigation

Utilizing electrolyte electroreflectance, we have developed a unique approach for determining the variations in composition x across the face of binary and ternary alloy semiconductors. This technique is based on the fact that the energies of features in the optical spectra of semiconducting alloys depend on x in a continuous manner. Any shift in energy of a particular electroreflectance peak is measured using a small scanned light spot. Corresponding variations in x can be determined to within about 1% with a spatial resolution of about 100 μm. This technique is nondestructive and can readily be employed under atmospheric conditions at room temperature. Results are presented for a number of alloys, including Hg1−xCdxTe, Ga1−xAlxAs, InAsxSb1−x, and Pb1−xSnxTe. The advantages of our approach in relation to microprobe or luminescence methods is discussed.