Improving the Brightness and Reliability of InGaN/GaN Near Ultraviolet Light-Emitting Diodes by Controlling the Morphology of the GaN Buffer Layer

A facile method for fabricating near ultraviolet light-emitting diodes (NUV LEDs) with better crystal quality and enhanced light emission is demonstrated by tuning total working pressure to modify the morphology of the buffer layer. With the conditions favoring the transition from 2-D to 3-D island growth in the GaN buffer layer, the crystal quality of the epitaxial GaN film is improved, leading to a decrease in the full-width at half-maximum of the (1 0 2) peak in $X$ -ray rocking curve measurement from 293 (arcsec) to 230 (arcsec). Scanning electron microscopy images imply the morphology of GaN grain boundaries at the buffer stage is different. The transmission electron microscopy analysis shows the edge dislocation can be bended due to the controlled morphology of buffer layer, leading to a better crystal quality of the GaN epitaxial film. Therefore, the reverse current is reduced with the reverse bias of $ - \hbox{40 V}$ . Moreover, the output power in lamp-formed NUV LEDs at a driving current of 20 mA can be enhanced by about 12%.