Reduction of strain and dislocation defects in GaN layers grown on Si substrate by MOCVD using a substrate defect engineering technique

We report on the application of a new scheme of substrate engineering in Si (I 11) substrate to obtain high quality GaN layers on Si substrates. An ion implanted defective layer is formed in the Si substrate that partially, crystallographically and mechanically isolates the III-Nitride layer and Si substrate which results in reduction of strain in the Nitride film. Nitrogen ion implantation energies of 60-75 keV and ion doses of 1 x 10(16) cm(-2)-2x 10(16) cm(-2) were applied to AIN buffer layers of 55 mn thick grown on Si (111). The experimental results show an increase in the crack separation of over 1 mm for 2 mu m thick GaN film grown on implanted 55 mn AIN/Si complex substrate as seen under optical microscope. Moreover the GaN films grown on implanted AIN/Si substrate showed smoother surface morphology (RMS roughness of 0.41 nm) as compared to that grown on non-implanted AIN/Si substrates (RMS roughness of 1.50 run). Results of etch pit density and XRD measurements show significant reduction in dislocations in III-Nitride layers. Our data shows a strong dependence of GaN quality on the implantation conditions. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.