Abstract
The GaN epitaxial films were prepared by metal-organic chemical vapor deposition (MOCVD) and grown on an Al2O3 substrate. A low-temperature GaN buffer layer was applied to overcome the large lattice mismatch between the GaN and the substrate. The p-type GaN epitaxial films were then grown by the reaction of NH3 and trimethyl gallium (TMGa). The biscyclopentadienyl magnesium (Cp2Mg) was used as the p-type doping precursor. The trimethyl Indium (TMIn) was used as the In doping precursor. The flow rates of introducing Cp2Mg and TMIn were varied from 100 sccm to 500 sccm in this study. A growth rate of 1~2μm was achieved during the growth cycle.The SIMS depth profiles were obtained using a CAMECA ims-4f SIMS. The primary beam was 8 keV O2+ with a current of 130 nA. To minimize the sample charging, the surface of GaN was coated with a thin gold layer and an electron flood gun was employed during the SIMS measurement. Depth profiles of 24Mg+, 16O+, 14N+, 115In+, and 138Ga2+ were obtained for each sample. The results showed that the growth rate decreased with increasing Mg doping. The doping of In decreased the growth rate and Mg concentration. Mg standards were prepared using ion implantation to determine the RSF required for Mg quantification in GaN films. The total Mg content in GaN was determined using NAA.The SEM and AFM results indicated that In worked as the surfactant to improve the GaN quality in the epitaxy process, resulting in decreasing surface roughness with In doping.