Epitaxial growth of GaN with a high growth rate of 1.4 μm/h by RF-radical source molecular beam epitaxy

Abstract

GaN epitaxial layers were grown on (0001) sapphire substrates by molecular beam epitaxy (MBE) using RF radical nitrogen sources with relatively high growth rates of 1.2–1.4μm/h. For the growth rate around 1.2μm/h, the N2 flow rate was optimized, so that a low residual carrier density of GaN of 2.8×1016cm−3 and a smooth surface were obtained. The n-type Si-doping of GaN was demonstrated. The carrier densities of Si-doped GaN films were controlled in the range from 1.7×1017 to 1.5×1018cm−3 by changing the Si cell temperature. By increasing the amount of Ga and nitrogen supply, the maximum growth rate of 1.4μm/h was achieved at substrate temperature around 760°C. The surface morphologies were smooth but inferior to that of 1.2μm/h growth, because the growth condition for the growth rate of 1.4μm/h was not optimized yet. The residual carrier density was around 1×1017cm−3. The near band-edge emission was observed in both room temperature and 15K photoluminescence measurements.