Contactless mapping of mesoscopic resistivity variations in semi-insulating substrates

The lateral homogeneity of the electrical resistivity ρ of semi-insulating GaAs substrates is measured with high resolution using contactless capacitive mapping. The improved technique is capable of imaging mesoscopic ρ fluctuations correlated with the cellular structure of the dislocation density. The results compare favorably with data obtained by point contact topography. A measurement and statistical analysis procedure is described that allows an individual evaluation of the macro- and mesocopic contributions to the total on-wafer ρ variation.