GaN Films Grown on Si （111） Substrates Using a Composite Buffer with Low Temperature A1N Interlayer

A GaN interlayer between low temperature （LT） A1N and high temperature （PIT） A1N is introduced to combine HT AIN, LT A1N and composition-graded A1GaN as a novel buffer layer for GaN films grown on Si （111） substrates. The crystal quality, surface morphology and strain state of the GaN film with this new buffer are compared with those of GaN grown on a conventional buffer structure. By changing the thickness of LT A1N, the crystal quality is optimized and the crack-free GaN film is obtained. The in-plane strain in the GaN film can be changed from tensile to compressive strain with the increase in LT A1N thickness.