Interface roughness of double buffer layer of GaN film grown on Si(1 1 1) substrate using GIXR analysis

Abstract

A double buffer layer (DBL), interface reaction epitaxy (IRE) AlN/β-Si3N4/Si, grown by an IRE of β-Si3N4 and AlN films on Si, was fabricated to improve the crystalline quality of successively grown 30nm GaN on a 30nm AlN buffer layer using plasma-assisted molecular beam epitaxy (PA-MBE). The DBL was first prepared by surface nitridation of Si and successively prepared by IRE between the deposited Al and N atoms in β-Si3N4. Both the AlN buffer layer on the DBL and GaN film on the AlN buffer layer were grown by activity-modulation migration enhanced epitaxy (AM-MEE). Hetero epitaxial grown films of GaN(30nm)/AlN buffer(30nm)/DBL/Si(111) were prepared for analysis using a three layer model of grazing incidence-angle X-ray reflectivity (GIXR), which consisted of three layers of GaN, AlN buffer and Si and of the three interfaces of the GaN surface, GaN/AlN buffer and AlN buffer/DBL/Si. The nitridation temperature dependence of the interface roughness of the DBL was measured to be 0.5 and 0.6nm, for nitridation temperatures of 780 and 830°C, respectively. The full width at half maximum (FWHM) of rocking curve GaN(0002) measured by X-ray diffraction (XRD) for nitridation temperatures of 780 and 830°C were 58.2 and 55.2arcmin, respectively.