Surface morphology and optical properties of InGaN/GaN multiple quantum wells grown on freestanding GaN (0001) substrates

Abstract

Surface morphology and optical properties of InGaN-based multiple quantum wells grown on c-plane freestanding GaN substrates by metalorganic vapor phase epitaxy was investigated. The surface shows a dependence on the substrate crystallographic orientation, presenting wavy and mirror-like feature with the substrate off-cut towards the [112¯0] direction and the [11¯00] direction, respectively. To get sharp hetero-interfaces, InGaN multiple-quantum-wells-based blue laser diode wafers were grown on substrates with off-cut towards the [11¯00] direction. The photoluminescence peak wavelength of the blue laser wafers shows a linearly blue shift as the substrate off-cut angle increases. A minimum spectra line width of 90 meV@450 nm can be obtained with a substrate off-cut angle of about 0.5°. These surface and optical properties were ascribed to the step growth kinetics of the wurtzite type materials.