Patterned sapphire substrates cause a wavelength shift of green InGaN light-emitting diodes

InGaN/GaN multiple quantum wells (MQWs) were fabricated under the same growth conditions on the planar and patterned sapphire substrates (PSS) with 10 nm and 20 nm sputtering AlN layers, respectively. Photoluminescence and electroluminescence results both showed that MQWs samples have significant differences in emission wavelengths. The wavelength of the samples on planar substrate is about 20 nm longer than that on the PSS. For samples with the same substrate, but different AlN layer thickness, also exhibit a small wavelength shift. High-resolution X-ray diffraction also revealed that the periodic thickness of MQWs on a planar substrate is thicker than that on PSS. Thermodynamic simulation was carried out to verify the effect of PSS on the heat conduction of GaN film. The PSS embedded in GaN film will affect its heat dissipation ability, and thus influence the wavelength of the MQWs samples by affecting the growth temperature.