The progress of AlN bulk growth and epitaxy for electronic applications

Abstract

Abstract 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 to 30 arcsec 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 AlN substrates by organometallic vapor phase epitaxy (OMVPE). We have demonstrated pseudomorphic growth of graded Al 1– x Ga x N layers with a thickness of one order of magnitude higher than the expected critical thickness from the classical Matthews–Blakeslee theory. This achievement has resulted in low dislocation density AlGaN epi‐layers with both symmetric and asymmetric rocking curves routinely below 100 arcsec. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)