High-resolution optical detection of electron spin resonance in epitaxial semiconductor layers by coherent Raman spectroscopy

We describe the application to semiconductors of a microwave-frequency optical heterodyne technique that enables electron-spin-resonance spectra to be detected through coherent Raman scattering. The technique is sufficiently sensitive to detect spectra from epitaxial layers and has the added advantage of optical selectivity. We demonstrate its effectiveness with studies of a ZnSe epitaxial layer in which there is a variation in strain. The spin-resonance linewidths are sufficiently narrow for the gyromagnetic ratio to be determined with a precision of 1 part in 104 and, as the laser is tuned to resonance with differently strained parts of the material, the g value changes at a rate of approximately 0.4 eV–1. We have carried out the experiment in both transmission and reflection geometries and the technique promises to be of wide applicability.