Abstract: A method for nondestructively measuring dislocation density in a GaAs wafer is disclosed in which an unetched GaAs wafer is tested for fractional transmission (T) of light at a plurality of points over its surface. A light beam from a suitable source such as a tungsten-halogen lamp is passed through a monochromator and focused by a lens on the wafer. The fractional transmission (T) of light through the wafer is detected and the absorption coefficient (.alpha.) is calculated at each of the points from the detected values of the fractional transmission. Regions of dislocation density in the wafer are determined nondestructively from the absorption data by dividing the values of .alpha. into equal segments bounded by the minimum and the maximum calculated values. A histogram is plotted of the number of values of .alpha. in each segment versus the value of .alpha. at the midpoint of the segment. A reference .alpha.

Abstract: A method and system for measuring whole-wafer etch pit density (.rho..sub.D) is disclosed in which an etch GaAs wafer is tested for fractional transmission at a plurality of points over its surface. The fractional transmission (T) of light through the wafer is detected, amplified and fed to a computer where at least two points of transmission measurement are selected for calibration. From these measurements, together with an estimate of the average etch pit size (area), the values for fractional transmission in regions of low etch pit density T.sub.O and high etch pit density T.sub.E may be calculated, and used to convert transmission data directly to etch pit density (.rho..sub.