Growth and p-type doping of GaN on c-plane sapphire by nitrogen plasma-assisted molecular beam epitaxy

Abstract

Effect of III/V ratio on the quality of GaN epilayers has been investigated. GaN films were grown on the c-plane of sapphire by using radio frequency (RF) nitrogen plasma-assisted molecular beam epitaxy (MBE). A home-made III-V nitride MBE system consisted of an inductively coupled RF nitrogen plasma source and solid source effusion cells were used to grow GaN films. The results of reflection high energy electron beam diffraction (RHEED) and double crystal X-ray diffraction indicate that crystal quality of GaN epilayers is strongly dependent on the Ga flux. Room temperature photoluminescence spectrum of undoped GaN epilayer is peaked at 3.39 eV and no discernible yellow luminescence resulting from ion damages are observed. Effect of Mg flux on the carrier concentration of p-GaN have also been investigated. Fairly uniform p-doping concentration as high as 5.33 x 10 18 /cm 3 throughout the GaN crystal were obtained. The sample grown with T Ga = 900°C and T Mg = 130°C exhibits very streaky RHEED patterns and the highest p-type doping concentration.