HIGH-SENSITIVITY COMPUTER-CONTROLLED INFRARED POLARISCOPE

A high-sensitivity computer-controlled infrared polariscope has been developed to measure a small amount of phase retardation, and the principal axes of birefringence induced by residual strains in commercial III-V compound wafers with standard dimensions. In order to check the performance of the polariscope, semi-insulating LEC-grown GaAs (100) wafers, currently used for high-speed integrated circuits, were examined. The residual strain components of \S(r) - S(t)\, \S(yy) - S(zz)\, and \S(yz)\ were evaluated from the measured values of the phase retardation and the principal axes of birefringence. It was found that the polariscope developed here was highly sensitive enough to characterize the residual strain components to the order of 10(-7) in thin commercial GaAs wafers.