The study of light-emitting diode fabricated on c-axis patterned and flat sapphire substrate

GaN thin films and multi-quantum wells (MQWs) were grown on the c-axis patterned sapphire substrates and c-axis flat sapphire substrates by metal organic chemical vapor deposition, respectively. The surface morphology of patterned sapphire substrate and flat sapphire substrate were measured by scanning electron microscopy. The crystal structure of GaN thin films and MQWs were measured by X-ray. The optical performance of MQWs was measured by photoluminescence spectra. The residual stress of GaN thin films was studied. GaN thin films on patterned sapphire substrate has a better crystalline quality in the [102] direction than that on flat sapphire substrate. The residual stress in MQWs on PSS is delta(xx) = 1.10 GPa, delta(yy) = 0.13 GPa, while the residual stress of films on FSS is delta(xx) = 0.83 GPa, delta(yy) = 0.10 GPa. It is found that the wavelength becomes shorter and the emission intensity becomes stronger on patterned sapphire substrate.