High quality GaN epilayers grown on Si (1 1 1) with thin nonlinearly composition-graded Al xGa 1− xN interlayers via metal-organic chemical vapor deposition

Abstract

The growth of GaN epilayers on AlN/Si (1 1 1) templates with thin nonlinearly composition-graded Al x Ga 1− x N interlayers via metal-organic chemical vapor deposition (MOCVD) is reported in this work. The composition-graded Al x Ga 1− x N interlayer was achieved by simply changing the growth condition of AlN to that of GaN layers during a fixed time. The surface morphology, crystalline quality and stress of GaN films have been investigated with different Al x Ga 1− x N interlayer thickness, 280 nm, 460 nm, 575 nm, and 750 nm. It was found that the properties of GaN films are highly dependent on the Al x Ga 1− x N interlayer thickness. High quality crack-free GaN films up to 1.2 μm can be achieved with 460 nm thick Al x Ga 1− x N layer.