Stress Analysis of GaN-Based Heterostructures on Silicon Substrates

Elastic stresses in AlN layers on silicon substrates of different thickness, as well as in multilayer (Al, Ga)N structures grown on AlN/Si templates, were investigated based on in-situ reflectometry/deflectometry data. It was found that tensile stresses arise during the growth of AlN, with their magnitude increasing with thicker the substrate. During the growth of multilayer step-graded (Al, Ga)N structures, all layers underwent compressive stress which decreased towards the surface. After cooling the structures to room temperature, some of the lower AlGaN layers remained entirely compressed, while another part experienced both compressive (in the lower part of each layer) and tensile (in the upper part of each layer) stresses.