High-Performance Vertical Light-Emitting Diodes with Buried Current Blocking Layer and Non-Alloyed Reflective Cr/Al/Pt/Au n-type Electrodes

Abstract

A GaN-based vertical light-emitting diode (VLED) with a novel structure, consisting of a buried current blocking layer (BCBL) inserted in p-type GaN and non-alloyed reflective n-type electrodes (Cr/Al/Pt/Au) on N-face n-GaN, is proposed and its enhanced light extraction efficiency is demonstrated. It was found that this new VLED structure could significantly increase the light output power by about 16% compared to that of the conventional VLED chips with n-type Cr/Au electrodes and without the BCBL, although the use of the BCBL slightly increased the forward voltage. The increase in the light output power was attributed to the injection of a large current density within the emission region of the active layers by the BCBL and, thus, the reduction of the optical absorption beneath the n-pad electrodes by the Cr/Al/Pt/Au metals.

Realization of high-power dimmable GaN-based LEDs by hybrid integration with AlGaN/GaN HFETs

“…7(b), increased by more than 4 times with increasing V GS from −4 to −3 V at a V DD of 3.5 V. Furthermore, the on-state resistance (R on ) of the high-power dimmable VI-LEDs by integration with HFETs decreased from 15 to 8.7 Ω with increasing V GS form −3.5 to −3 V by using a linear extrapolation method, which can be due to the reduced resistance of 2DEG with increasing V GS from −3.5 to −3 V. 28) It is worth noting that the LOP of the VI-LEDs was as high as 379 mW at V GS of −3 V and V DD of 5 V for HFET, which is more than two orders of magnitude higher value than the previously reported LOP of monolithically integrated LED with HFET using SEG (1 mW at V GS of −3 V and V DD of 5 V). 19,20) This result can be attributed to the high forward current of 270 mA for the hybrid integration of VI-LED with HFET when compared to that of only 15 mA for the monolithically integrated LEDs with HFET. 29,30) This implies that the high-power dimmable GaN-based VI-LEDs can be realized through hybrid integration of VI-LED with AlGaN/GaN HFET, which is promising candidate for novel applications such as underwater VLC and adaptive headlights for vehicles.…”

“…This study focused on the realization of high-power dimmable GaN-based LED light sources with a small form factor by hybrid integration with AlGaN/GaN HFETs. For this purpose, the hybrid integration of GaN-based verticalinjection LEDs (VI-LEDs) with AlGaN/GaN-based HFETs having multi-level metallization via the flip-chip bonding technique was examined, because VI-LEDs can yield a high power over 100 mW at a forward current of 100 mA [16][17][18][19][20] and AlGaN/GaN-based HFETs with multi-level metallization can give a high current over 1 A at V GS of 1 V and V DS of 2 V with much smaller form factor than the conventional HFETs. [21][22][23] Furthermore, the flip-chip bonding method will not reduce the efficiency of the integrated LED and HFET devices because it does not apply the SEG and SER processes.…”

Electrochemical potentiostatic activation for improvement of internal quantum efficiency of 385-nm ultraviolet light-emitting diodes

“…The low-cost fabrication of high-efficiency LED chips is considered as a fundamental requirement for GaN-based solid-state lighting. Many approaches have been studied in order to meet these requirements, such as epitaxial growth on largearea silicon substrates, the use of non-polar sapphire substrates, and advanced chip designs, like vertical chips [2][3][4][5][6]. Poor quality of the p-type GaN layer is one of the main obstacles that hinder the achievement of high efficiency.…”