Crystallographic Tilt in Aluminum Gallium Nitride Epilayers Grown on Miscut Aluminum Nitride Substrates

Heteroepitaxial crystallographic tilt has been investigated as a possible strain-relief mechanism in Al-rich (Al>50%) AlGaN heteroepitaxial layers grown on single-crystal (0001) AlN substrates with varying miscuts from 0.05 degrees to 4.30 degrees. The magnitude of the elastic lattice deformation-induced tilt increases monotonically with the miscut angle, tightly following the Nagai tilt model. Although tilt angles as high as 0.1 degrees are recorded, reciprocal space mapping (RSM) broadening and wafer bow measurements do not show any significant changes as a function of the heteroepitaxial tilt angle. While crystallographic tilting has been shown to be effective in controlling strain in some other heteroepitaxial systems, it does not provide any appreciable strain relief of the compressive strain in AlGaN/AlN heteroepitaxy.