Growth of crack-free AlGaN film on high-temperature thin AlN interlayer

Abstract

We report on successful fabrication of crack-free thick AlGaN layers by introducing a thin AlN interlayer at the high temperature of 1000–1100°C on a high quality GaN epitaxial layer. The Al 0.52Ga 0.48N films grown with the optimized AlN interlayer exhibited mirror-like surface morphology and were free of cracks up to the thickness of 3 μm. X-ray analyses and cathodoluminescence spectra showed excellent structural and optical quality of the AlGaN materials. Si-doped n-type AlGaN films were also grown on the high-temperature AlN interlayer, and excellent n-type conductivity was achieved up to Al 0.38Ga 0.62N with the electron concentration of 2.0×10 18 cm −3 and the mobility of 79 cm 2/V s. Furthermore, from monochromatic cathodoluminescence images, we proposed that initial cracking of the AlN interlayer reduces the residual stress, thus preventing cracking in the AlGaN layer by generating misfit dislocations at AlGaN/AlN interface.