Improving the External Quantum Efficiency of High-Power GaN-Based Flip-Chip LEDs by Using Sidewall Composite Reflective Micro Structure

Abstract

For high-power applications, it is important to improve the light extraction efficiency and light output of the vertical direction of LEDs. Flip-chip LEDs (FCLEDs) with an Ag/SiO2/distributed Bragg reflector/SiO2 composite reflection micro structure (CRS) were fabricated. Compared with the normal Ag-based FCLEDs, the light output power of the CRS-FCLEDs was increased by 6.3% at an operational current of 1500 mA, with the corresponding external quantum efficiency improved by 6.0%. Further investigation proved that the CRS structure exhibited higher reflectance compared with the commonly used Ag-mirror reflective structure, which originates from the increased reflective area in the sidewall and partial area of the n-GaN contact orifices. It exhibited markedly smaller optical degradation and thus higher device reliability as compared to normal Ag-based FCLED. Moreover, the light emission intensity distributions and far-field angular light emission measurements show that the CRS-FCLED has a strengthened light output in the vertical direction, which shows great potential for applications in high-power fields, such as headlamps for automobiles.

An AlGaN/GaN Lateral Bidirectional Current-Regulating Diode with Two Symmetrical Hybrid Ohmic-Schottky Structures

“…Although AlGaN/GaN CRDs are scarcely reported, developing a high-performance power electronic system based on AlGaN/GaN CRDs is of great potential. For example, high-performance single-chip LED lighting systems could be achieved through monolithically integrating AlGaN/GaN CRDs with GaN-based LEDs [ 11 , 12 ]. Furthermore, owing to their wide bandgap, AlGaN/GaN CRDs are also preferred for battery charge/discharge in harsh environments.…”

Editorial for the Special Issue “Microsystem for Electronic Devices”

“…This Special Issue includes 12 high-quality papers focused on the development of microsystems. Half of the published papers focus on light-emitting diode (LED) microsystems and related microelectronic systems [4][5][6][7][8][9], three papers discuss the cooling techniques of electronic microsystems [10][11][12], and the final three papers present several mechanical microsystems [13][14][15].…”

“…This technique represents a promising direction for fabricating highperformance microstructure-based color converters. Guo et al [7] fabricated flip-chip light-emitting diodes with a composite microstructure comprising Ag/SiO 2 /distributed Bragg reflector/SiO 2 to enhance light extraction efficiency and vertical light output for high-power applications. The composite reflector exhibits a higher reflectance compared to the commonly used Ag-mirror reflective structure, which is due to the increased reflective area in the sidewall and partial area of the n-type gallium nitride contact orifices.…”