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

Abstract

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: 1000×1000µm2) and large (1450×1450µm2) VLEDs, the forward bias voltages are decreased from 3.22 to 3.12V at 350mA and from 3.44 to 3.16V at 700 mA, respectively, as the number of n-contact via holes is increased. The small LEDs give maximum output powers of 651.0–675.4mW at a drive current of 350mA, while the large VLEDs show the light output powers in the range 1356.7–1380.2mW, 700mA, 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.