Improvements of N-Side-up GaN Light-Emitting Diodes Performance by Indium–Tin-Oxide/Al Mirror

Abstract

An n-side-up vertical conducting GaN/mirror/Si light-emitting diode (LED) has been fabricated using a combination of wafer-bonding, laser lift-off, and surface texturing techniques. The indium–tin-oxide (ITO)/Al and Pd mirror were chosen to improve optical reflectivity and contact resistance with p-GaN. It was found that the LEDs with higher reflectivity mirrors present better optical properties. A GaN/ITO/Al/Si LED with surface texturing presents maximum luminance intensity with five times the magnitude of the original planar GaN/sapphire LED at 20 mA. The output power characteristic of a GaN/ITO/Al/Si LED is 8.9 mW, and it is higher than that of the original GaN/sapphire (4.5 mW) LED at 20 mA. With high current injection, the surface textured GaN/ITO/Al/Si LED also shows more stable luminance intensity and output power. The junction temperature is measured by the diode forward method. As the dc forward current increases to 200 mA, the junction temperatures of the GaN/mirror (ITO/Al)/Si and GaN/sapphire LED are 87 and 158 °C, respectively. Obviously, the Si substrate provides good thermal dissipation.