EFFECT OF THE TRIMETHYLGALLIUM FLOW DURING NUCLEATION LAYER GROWTH ONTHE PROPERTIES OF GAN GROWN ON SAPPHIRE

We report on the effect of the trimethylgallium Bow during nucleation layer growth on the electrical; optical and structural properties of e pitaxial GaN films grown on basal plane sapphire by atmospheric pressu re metalorganic chemical vapor deposition. The 1.2 mu m thick GaN film s grown on nucleation layers with the optimum trimethylgallium flow of 45 mu mol/min had a room temperature mobility of 644 cm(2)/s and mini mum width of the (002) and the (102) X-ray diffraction peaks. The roug hness of the as-grown nucleation layers decreased with increased trime thylgallium Bow. However, smooth, as-grown, nucleation layers showed a strong tendency for island coarsening and an increased surface roughn ess after heating to the bulk GaN growth temperature.