Silicon-induced strain relaxation and enhanced gallium surfactant effects on gallium nitride island shaping

The self-organization of large-scale uniform aligned three-dimensional GaN nanoislands with triangular (0001) and distinct sidewall faceting has been realized by metal organic vapor-phase epitaxy on in situ Si-rich SiNx nanoislands patterned c-sapphire substrates. We find that the GaN island shaping is closely related to the SiN, pretreatment chemistry. It is suggested that enhanced surface Ga surfactant effects and compressive strain relaxation caused by site exchanges between excess Si and subsurface Ga atoms are responsible for the distinct triangular island shaping with large lateral size, smooth sidewall facets, and sharp triangle corners. Photoluminescence studies also show Si-doping-induced compressive strain relaxation and improved crystalline qualities for triangular GaN islands grown with the Si-rich SiNx pretreatment.