Enhancement of light output power of GaN-based vertical light emitting diodes by optimizing n-GaN thickness

The light output and electrical characteristics of GaN-based vertical light emitting diodes were investigated as a function of n-GaN thickness. The forward voltage increases from 3.34 to 3.42 V at an injection current of 350 mA as the n-GaN thickness decreases from 5.0 to 2.0 μm. Even at a high injection current of 2.0 A, LEDs with 2.0 μm-thick n-GaN reveal stable forward characteristics which are comparable to those of LEDs with 5.0 μm-thick n-GaN. All the samples exhibit almost the same reverse current up to approximately -8 V. The output power increases with decreasing n-GaN layer thickness. For example, LEDs with 2.0 μm-thick n-GaN yield about 12% higher light output power as compared to LEDs with 5.0 μm-thick n-GaN. Their light output power continuously increases without saturation as the injection current increases up to 1 A. The n-GaN thickness dependence of the electrical characteristics is described and discussed.