Improving Emission Uniformity of InGaN/GaN-Based Vertical LEDs by Using Reflective ITO/Ag n-Contact

Abstract

We investigated the effect of Ti/Al and ITO/Ag n-type contacts on the emission uniformity and light output of different chip-size vertical-geometry light-emitting diodes (VLEDs) for vehicle headlamp application. The forward voltage of the Ti/Al-based reference VLEDs decreased from 3.38 to 3.20 V at 1500 mA with increasing chip size from (1280 × 1000 µm2) to (1700 × 1700 µm2), whereas that of the ITO/Ag-based samples changed from 3.37 to 3.15 V. Regardless of chip size, the ITO/Ag-based samples revealed higher light output power than the reference samples. For example, the ITO/Ag-based samples (chip size of 1700 × 1700 µm2) exhibited 3.4% higher light output power at 1500 mA than the reference samples. The ITO/Ag samples underwent less degradation in the Wall-plug efficiency (WPE) than the reference sample. For instance, the ITO/Ag-based samples (1700 × 1700 µm2) gave 4.8% higher WPE at 1500 mA than the reference samples. The ITO/Ag-based samples illustrated more uniform emission than the Ti/Al-based sample. Both the reference and ITO/Ag-based samples underwent no degradation when operated at 1500 mA for 1000 h.

Numerical Model of Current Flow and Thermal Phenomena in Lateral GaN/InGaN LEDs

“…It causes intensive investigation of their design, technology, and features, carried out by both by industry and university research teams. The studies focus on different design concepts such as vertical [1][2][3], lateral [4,5] or 3D core-shell [6][7][8][9] devices, discussing their fabrication technologies [10][11][12], or aiming at their features employing experimental [13,14] or numerical [15][16][17] approaches.…”