STUDY OF INTERFACE STRESSES IN HETEROSTRUCTURES USING INFRARED PIEZOBIREFRINGENCE

A general algorithm for the simulation of stress field images in III-V heterostructures, using infrared piezobirefringence, is presented in this article. As a first step, the algorithm is applied for the simula tion of stress fields associated with step deposited SiO2 on GaAs subs trates, under two assumptions-one that of distributed loading along th e film, and the other that of concentrated loading at the two edges of the film. The simulated images are presented, and these are seen to b e functions of film and sample thicknesses, and polarization angle of the incident light. Next, the algorithm was applied for III-V heterost ructures (with and without misfit dislocations), and the simulated ima ges are presented. These images are functions of substrate thickness, film thickness, dislocation density at the interface, and polarization angle of the incident light. In principle, any arbitrary heterostruct ure can be placed under a dark field polariscope. and the experimental images of the interface obtained for varying polarization angles of t he incident light. Then an image matching procedure between the experi mentally observed images and the simulated ones can yield the informat ion about the defects present at the interface. This technique offers a superior speed advantage over other conventional methods, and permit s testing of each individual sample without going in for statistical e stimates. This can tremendously boost the yield. Some experimental res ults and their match with the theoretical ones are also presented. (C) 1996 American Institute of Physics.