Effects of AlN interlayer on growth of GaN-based LED on patterned silicon substrate

Abstract

GaN-based light emitting diodes (LEDs) were grown on 1 mm × 1 mm patterned 2-inch and 6-inch Si (111) substrates by metal–organic vapour phase epitaxy (MOVPE). AlN interlayers with different thicknesses were introduced between the composition-graded AlGaN buffer layer and the GaN seed layer in different LED structures. The crystalline quality, wavelength uniformity and crack density of the 2-inch wafer were improved by increasing the AlN interlayer thickness. With a 30 nm AlN interlayer, a crack-free, smooth and reflective 6-inch LED wafer was grown, the full width at half maximum (FWHM) of the XRD rocking curves of GaN (002) and GaN (102) planes were 384 and 432 arcsec, respectively. The standard deviation of thickness and dominant wavelength were 0.03 μm (average thickness was 3.84 μm) and 1.52 nm (average dominant wavelength was 457.9 nm), respectively. The AlN interlayer can change the growth mode of the GaN seed layer and subsequent n-GaN, which changes the density of dislocation and the residual tensile stress of the GaN film. A smaller residual tensile stress in the GaN film can help to reduce bowing of the wafer, improve the wavelength uniformity, and suppress the generation of cracks.