Optically induced far‐infrared absorption from residual acceptors in as‐grown GaAs

Far‐infrared Fourier transform spectroscopy has been applied to study residual shallow acceptors in as‐grown semi‐insulating GaAs. Secondary optical excitation into the EL2 absorption band has been used to create a nonequilibrium hole population to neutralize the acceptors. Optically induced absorption spectra from carbon and zinc acceptors have been observed. The dependence of these spectra on the secondary illumination is studied. A comparison is made with electronic Raman spectra recorded from the same samples.