Pattern-size dependence of characteristics of nitride-based LEDs grown on patterned sapphire substrates

Abstract

Micro- and nano-scale patterned sapphire substrates (PSS) were fabricated by conventional photolithography and nanosphere lithography, respectively. Nitride-based light-emitting diodes (LEDs) were grown on different pattern sizes of patterned sapphire substrates, and the structural, electrical, optical properties of these LEDs were investigated throughout. The structural properties clearly indicate that the crystalline quality of epitaxial GaN film could be effectively improved by using the PSS technique. The leakage current is related to the crystalline quality of epitaxial GaN film, and it was also improved by using the PSS technique. The forward voltages of the LEDs grown on different pattern sizes of the PSS were similar. The light output power and external quantum efficiency of the LED grown on nano-scale of the PSS was the largest in all the samples. It indicates that the pattern size of the PSS is related to the capability of light extraction.