InGaN multiple-quantum-well light-emitting diodes on an AlN/sapphire template by metalorganic chemical vapor deposition

An InGaN multiple-quantum-well (MQW) LED grown on AlN/sapphire template is reported. Comparing with the conventional LED on sapphire using a low temperature (LT) buffer layer, the LED on AlN/sapphire template shows better electrical and optical characteristics. The crystalline quality of the LED structure was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The zeroth, -first-and-second-order satellite peaks and the Pendellösung fringes can be seen clearly in (0004) XRD ω/2θ rocking curves for the LED on AlN/sapphire template. While, for the LED on sapphire, only the zeroth and -first-order satellite peaks can be seen. The full width at half maximum (FWHM) of GaN in (0004) ω scan is about 82.8 and 231.6 arcsec for the LED grown on AlN/sapphire template and sapphire, respectively. The dislocation density is 5 × 10⁷-3 × 10⁸ cm^-2 for the LED on AlN/sapphire template and 2-5 × 10⁹ cm^-2 for the LED on sapphire. The reverse leakage current of the LED on AlN/sapphire template is over one order of magnitude lower than that on sapphire due to the low threading dislocation density in the epilayer. The optical power of the LED on AlN/sapphire template increased sublinearly up to 300 mA injection current.