Scanning birefringence mapping of semi-insulating GaAs wafers

Micron scale birefringence mapping of 1 cm/sup 2/ portions of 3" semi-insulating GaAs wafers shows fluctuations over characteristic dimensions between 50 and 500 /spl mu/m, with magnitudes as large as 1/5 wavelength. The results are compared to those of more familiar characterisation tools, scanning photolurninescence mapping and x-ray topography. Scanning birefringence mapping resolves some of the same features as the other techniques, for example through wafer strain free low angle grain boundaries, while containing unique information related to the strain in the wafer. A model for the observed correlation is presented, and implications for substrate electro-optic probing are discussed.