Evolution of crystal quality and stress in the early stages of GaN-on-Si (111) MOVPE with a single AlN buffer layer

As an important field of "III-V on Silicon" optoelectronic integration industry, GaN-on-Si has attracted intensive study for over two decades. Efforts are ongoing to identify effective strategies to realize high-quality and stress balanced GaN on Si. In order to understand its crystal quality and stress evolution mechanism during the metal- organic vapor phase epitaxy (MOVPE), this study focused on the early stages of the growth, i.e. the AlN buffer layer and the first overlying GaN layer, systematically investigated the effects of growth temperature and V/III ratio for AlN buffers and the growth mode of GaN layer. AlN buffer layer grown at 1250 degrees C and moderate V/III ratio around 3000 resulted in high crystal quality for both AlN buffer and GaN, and induced less tensile stress in AlN and more compressive stress in GaN. In growth mode comparison for GaN layer, GaN grown in threedimensional (3D) Volmer-Weber mode was of much better crystal quality while much less effective compressive stress introduction. It clarified that three stress inducing and relaxation mechanisms including lattice constant mismatch, interface quality and growth mode should be taken into account together for GaN-on-Si epitaxy structure design by considering the quality of GaN as well.