Improving Light Output of Vertical-Stand-Type InGaN Light-Emitting Diodes Grown on a Free-Standing GaN Substrate With Self-Assembled Conical Arrays

We demonstrated the fabrication and study of vertical-stand-type homoepitaxial light-emitting diodes (VLEDs) on a GaN substrate with conical array structures. The conical arrays were formed on the N-face surface of the GaN substrate using a size-controllable polystyrene nanosphere as etch mask. The 20-mA output power of the VLEDs with flat backside, truncated cone, and cone arrays improved by magnitudes of 16.5%, 66.8%, and 118.5%, respectively, compared with that of conventional planar configuration LEDs. These improvements could be attributed to the increased direct illumination surface and reduction in photon extraction path length. Moreover, small wavelength redshift proved that the VLED on the GaN substrate did not suffer from serious thermal effect.