GROWTH AND P-TYPE DOPING OF GAN ON C-PLANE SAPPHIRE BY NITROGEN PLASMA-ASSISTED MOLECULAR-BEAM EPITAXY

Effect of III/V ratio on the quality of GaN epilayers has been investi gated, 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 coupl ed RF nitrogen plasma source and solid source effusion cells were used to grow GaN films. The results of reflection high energy electron bea m diffraction (RHEED) and double crystal X-ray diffraction indicate th at crystal quality of GaN epilayers is strongly dependent on the Ga fl ux. Room temperature photoluminescence spectrum of undoped GaN epilaye r is peaked at 3.39 eV and no discernible yellow luminescence resultin g from ion damages are observed. Effect of Mg flux on the carrier conc entration of p-GaN have also been investigated. Fairly uniform p-dopin g concentration as high as 5.33 x 10(18)/cm(3) throughout the GaN crys tal were obtained. The sample grown with T-Ga = 900 degrees C and T-Mg = 130 degrees C exhibits very streaky RHEED patterns and the highest p-type doping concentration.