Comparison between optical techniques for the measurement of the surface electric field in (100) oriented GaAs

Three optical spectroscopic techniques commonly used for the measurement of the surface electric field (SEF) of semiconductors, namely photoreflectance (PR) near the E0 energy and near the E1 energy, and the linear electro-optic (LEO) effect of reflectance difference spectroscopy near the E1 energy, are compared on a series of (100) oriented GaAs layered structures. The LEO strength is found to be linearly proportional to the SEF obtained from the PR oscillation period near the E0 energy for samples with a single space charge region in which the field is uniform over the light penetration depth near E1(∼20 nm). The LEO strength remains proportional to the SEF for samples with multiple space charge regions while the PR period near E0 no longer reflects the true SEF. The SEF value estimated from the line width of PR near the E1 energy is quite unreliable because both the electric field and the impurity scattering broaden the line.Three optical spectroscopic techniques commonly used for the measurement of the surface electric field (SEF) of semiconductors, namely photoreflectance (PR) near the E0 energy and near the E1 energy, and the linear electro-optic (LEO) effect of reflectance difference spectroscopy near the E1 energy, are compared on a series of (100) oriented GaAs layered structures. The LEO strength is found to be linearly proportional to the SEF obtained from the PR oscillation period near the E0 energy for samples with a single space charge region in which the field is uniform over the light penetration depth near E1(∼20 nm). The LEO strength remains proportional to the SEF for samples with multiple space charge regions while the PR period near E0 no longer reflects the true SEF. The SEF value estimated from the line width of PR near the E1 energy is quite unreliable because both the electric field and the impurity scattering broaden the line.