Influence of stress on structural properties of AlGaN/GaN high electron mobility transistor layers grown on 150 mm diameter Si (111) substrate

Abstract

Effects of stress imposed by individual nitride layers on structural properties of an AlGaN/GaN high-electron-mobility-transistor (HEMT) structure, which was grown on a 150 mm diameter Si (111) substrate by metal-organic chemical vapor deposition employing high-temperature step-graded AlxGa1−xN/AlN buffer layers, were studied using transmission electron microscopy, visible micro-Raman spectroscopy, and high-resolution x-ray diffraction. It is revealed that all the nitride layers are more or less tensile strained on the Si (111) substrate; however, strain relaxations occurred at all the heterointerfaces except for the AlGaN/(AlN/)GaN two-dimensional electron gas interface, which is desired for achieving high performance HEMT. The wafer curvature, an important parameter for large area epitaxy of GaN-on-Si, is modeled on the basis of stress distribution within individual layers of the multilayered AlGaN/GaN HEMT structure via the close-form expression developed by Olsen and Ettenberg [J. Appl. Phys. 48, 2543 (1977)]. The evolution of wafer curvature induced by substrate thinning and stress redistribution is predicted by this model, which is further qualitatively confirmed by experimental results.