Fabrication of vertical-structured GaN-based light-emitting diodes using auto-split laser lift-off technique

Vertical-structured GaN-based light-emitting diodes (V-LEDs) were successfully fabricated using auto-split laser lift-off (LLO) technique. Compared to regular sapphire-substrate LED, the forward voltage of the V-LED at 20 mA is about 5% lower, while the light output power is about 43% higher. For V-LED, the saturation behavior of the light output power (Lop) is not observed when the injection current is increased to 480 mA, while the Lop of regular LED starts to decrease at around 110 mA. These improved results can be attributed to the total effect of less current crowding, surface roughening on n-GaN layer, highly reflective Ag mirror and good thermal conductivity of the electroplated Ni. Finally, mechanisms of the auto-split LLO technique are discussed based on one-dimensional heat equation. It is shown that the auto-split LLO process is determined by the vapor pressure of N2 gas, which is strongly dependent on the density of the laser energy.