Spatial distribution of residual shallow acceptors in undoped semi-insulating GaAs

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Abstract
The spatial distribution of residual shallow acceptors in undoped semi-insulating GaAs has been studied quantitatively by electronic Raman scattering with a spatial resolution of ∼50 μm. This acceptor distribution has been correlated with the spatial distribution of the compensating EL2 donor in its neutral charge state measured by near-IR absorption topography. An enhanced acceptor concentration is found in regions which show high-IR absorption: From the comparison with low-temperature cathodoluminescence results, it is found that the intensity of the band-to-acceptor recombination normalized to the band-to-band luminescence intensity reproduces the acceptor distribution measured by Raman scattering. Implications of the present result on the compensation model for undoped semi-insulating GaAs are discussed.