Alumina-rich spinel: A new substrate for the growth of high quality GaN-based light-emitting diodes

A new substrate material, alumina-rich spinel, with better thermal and lattice match to GaN than sapphire, has been developed for growing high-quality GaN-based light-emitting diodes (LEDs). As 1:3 spinel (1 MgO for 3 Al 2O 3), MgAl 6O 10, is chemically close to sapphire, Al 2O 3, we successfully replicated on (1 1 1)-oriented spinel wafers the GaN metal-organic chemical vapor deposition conditions developed for c-plane sapphire. This enabled the simultaneous growth of GaN on both substrates. The resulting GaN layers are structurally, optically and electrically as good on 1:3 spinel as on sapphire. We therefore grew, still simultaneously on both substrates, InGaN LEDs with peak emission wavelengths ranging from 450 nm (blue) to 550 nm (yellow–green). Their electroluminescence (EL) was found to be brighter on 1:3 spinel than on sapphire, with the light output increasing almost linearly prior to breakdown in both cases. The EL full-width at half-maximum was also systematically narrower on 1:3 spinel than on sapphire, again confirming the high quality of the LEDs grown on this new substrate material.