The progress of AlN bulk growth and epitaxy for electronic applications

We report on the progress of high quality AlN bulk crystal growth by the sublimation-recondensation technique and present a theoretical model for optimizing the growth conditions. The theoretical model is consistent with our experimental findings and projects a path to maximize the growth rate by adjusting the growth temperature, external nitrogen pressure and source-to-seed distance. The growth of large AlN boules has resulted in the demonstration of crack-free AlN wafers up to 2-inch diameter. The crystallinity of these AlN boules and wafers has been characterized by X-ray techniques and etch pit density (EPD) measurements. The AlN wafers exhibited X-ray rocking curves with a full width at half maximum (FWHM) close 10 30 aresec for both symmetric and asymmetric curves with a corresponding EPD of < 10(4) cm(-2). High quality homoepitaxial and graded AlGaN layers have been grown on these IN substrates by organometallic vapor phase epitaxy (OMVRE). We have demonstrated pseudomorphic growth of graded Al1-xGaxN layers with a thickness of one order of magnitude higher than the expected critical thickness from the classical Matthews-Blakeslee theory. This achievement has results in low dislocation density AlGaN epi-layers with both symmetric and asymmetric rocking curves routinely below 100 arcsec. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim