UV Light-Emitting Diode Fabricated on Hetero-ELO-Grown Al0.22Ga0.78N with Low Dislocation Density

Using a hetero-epitaxial lateral overgrowth (ELO) technology with low-temperature deposited AlN interlayer, high-quality crack-free Al0.22Ga0.78N with low dislocation density is realized. The dislocation density in the Al0.22Ga0.78N was reduced to as low as the order of 107 cm—2 over the whole wafer. Applying the high-quality AlGaN layer to a UV light-emitting diode (LED), high output power of more than 0.1 mW at a forward current of 50 mA has been demonstrated with the emission peak wavelengths from 323 to 352 nm. The highest output power of 0.6 mW is obtained for the 352 nm LED with GaN/AlGaN multiple quantum well active layer. The emission efficiency was dependent on the wavelength, and the 323 nm LED has the lowest output power of 0.18 mW at 50 mA bias. One of the factors determining the external quantum efficiency is thought to be an inferior hole spread in highly resistive p-type layers.