The Influence of Crystalline Orientation on the Photoelastic Property of {100} Gallium Arsenide Wafer.

Abstract

We developed an optical birefringence measurement method that uses a photoelastic modulator and a polarized laser. A He-Ne infrared laser was utilized as the light source for measuring the birefringence in gallium arsenide wafers. In this paper we will explain the theory behind this method and the process of measuring the stress in GaAs wafers. The magnitude of the principal stress difference as well as the directions of the principal stresses were obtained simultaneously and quantitatively by using equipment developed for this study. The optical birefringences of stressed GaAs specimens were measured. From the experimental results, it was found that the photoelastic constant depended upon the crystalline orientations. Furthermore, the birefringence direction did not always coincide with the principal stress direction. The relationship between the principal strain difference and the retardation was obtained by the stress-strain analysis of a single GaAs crystal. That relationship was almost independent of the crystalline orientations and the birefringence direction was almost equal to the principal strain direction.