Optimizing n-type contact design and chip size for high-performance indium gallium nitride/gallium nitride-based thin-film vertical light-emitting diode

The effects of the n-contact design and chip size on the electrical, optical and thermal characteristics of thin-film vertical light-emitting diodes (VLEDs) were investigated to optimize GaN-based LED performance for solid-state lighting applications. For the small (chip size: 1000×1000 μm²) and large (1450×1450 μm²) VLEDs, the forward bias voltages are decreased from 3.22 to 3.12 V at 350 mA and from 3.44 to 3.16 V at 700 mA, respectively, as the number of n-contact via holes is increased. The small LEDs give maximum output powers of 651.0-675.4 mW at a drive current of 350 mA, while the large VLEDs show the light output powers in the range 1356.7-1380.2 mW, 700 mA, With increasing drive current, the small chips go through more severe degradation in the wall-plug efficiency than the large chips. The small chips give the junction temperatures in the range 51.1-57.2 °C at 350 mA, while the large chips show the junction temperatures of 83.1-93.0 °C at 700 mA, The small LED chips exhibit lower junction temperatures when equipped with more n-contact via holes.