Comparison of high quality GaN-based light-emitting diodes grown on alumina-rich spinel and sapphire substrates

High quality GaN-based light-emitting diodes (LEDs) can be achieved on alumina-rich spinel (MgAl6O10), a new substrate material with better thermal and lattice match to GaN than sapphire. As alumina-rich spinel is chemically very close to sapphire (Al2O3 the GaN metal-organic chemical vapour deposition (MOCVD) conditions developed for c-plane sapphire have been successfully replicated on it. In this article, we report on the electroluminescence (EL) properties of GaN-based LEDs grown by MOCVD simultaneously on Al2O3-(0001) and MgAl6O10-(111). Both devices exhibit a linear increase of the light output power versus current density, with a higher EL-intensity and a narrower EL-linewidth for the LEDs grown on alumina-rich spinel. However, due to the lower thermal conductivity of spinel, these LEDs start suffering from device heating at lower current densities than on sapphire. Irreversible damage occurs for DC current densities of similar to 0.9 kA/cm(2) and at an estimated junction temperature of similar to 325 degrees C. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.