Improved crystalline quality of GaN by substrate ion beam pre-treatment

GaN growth was carried out on Al/sub 2/O/sub 3/(0001) which was ion beam pre-treated to reduce the stain and dislocation density in the film. The ion dose was fixed to 1/spl times/10/sup 16/ ions/cm/sup 2/ and the ion energy used was 800eV and 5.5keV. The 800eV ion beam was reactive N/sub 2//sup +/ ions and the 5.5keV ion beam was from a normal ion implanter. Both ion beam pretreatments resulted in the formation of a disordered amorphous phase on the substrate surface. The GaN buffer and main growth was carried out by MOCVD,the strain was monitored using Raman spectra and dislocations were observed by TEM. The Raman shift clearly showed that the strain in the film was decreased by ion beam pre-treatment of sapphire prior to GaN deposition. The defect density in the film was reduced by up to 55% with ion beam pretreatment.