Vertical InGaN light-emitting diode with a retained patterned sapphire layer

Abstract

We present an efficient vertical InGaN light-emitting diode (LED) in which the proposed vertical LEDs were fabricated with patterned sapphire substrates (PSS) using thinning techniques. After the thinning of sapphire substrate, selective dry etching process was performed on the remainder sapphire layer to expose the n-GaN contact layer instead of removing the sapphire substrate using the laser lift-off technique. These processes feature the LEDs with a sapphire-face-up structure and vertical conduction property. The PSS was adopted as a growth substrate to mitigate the light-guided effect, and thereby increase the light-extraction efficiency. Compared with conventional lateral GaN LEDs grown on PSS, the proposed vertical LEDs exhibit a higher light output power and less power degradation at a high driving current. This could be attributed to the fact that the vertical LEDs behave in a manner similar to flip-chip GaN/sapphire LEDs with excellent heat conduction.

Micro Light‐Emitting Diodes for Display and Flexible Biomedical Applications

“…This review paper has described an overview of µLEDs for next‐generation displays and flexible biomedical devices . Implementation of high‐performance µLEDs have led to a wide range of technical advances in the fields of µLED device structures, performance enhancement, transfer processes, and packaging methods.…”

“…Copyright 2014, Royal Society of Chemistry. Right image: Reproduced with permission . Copyright 2012, OSA Publishing.…”

Coherent vertical beaming using Bragg mirrors for high-efficiency GaN light-emitting diodes

“…In the DBR, a quarterwave SiO 2 (n = 1.5) and TiO 2 (n = 2.5) were stacked in an alternating way over a specific period [18]. The DBR can be used in thin-film flip chip [19] or vertical slab GaN LEDs [3,5,10,12] where the sapphire substrate is removed by laser lift-off technique. First, we calculated the reflectivity of 2-pairs and 4-pairs of DBRs as a function of incident angle, and we also calculated the reflectivity of a silver mirror as a reference (Fig.…”

“…Thus far, several strategies for enhancing the light extraction efficiency of GaN LED devices have been proposed and demonstrated. The most common method for significantly increasing the light extraction efficiency is the introduction of random surface texturing [4,5] or periodic patterning into a GaN layer [3,6,7], bottom reflector [8,9], or substrate [10]. The non-periodic or periodic patterns can even diffract light waves whose wave vectors are outside the light cone (e.g.…”

Light Extraction Enhancement of GaN LEDs by Hybrid ZnO Micro-Cylinders and Nanorods Array

“…Most generated photons are confined inside the LED and absorbed by the LED-chip, degrading the device efficiency [3]. Therefore, much effort has been devoted to improve the LEE of GaN-based LEDs for high-brightness, including photonic crystals [4], surface texturing [5], flip-chip LEDs [6] and patterned sapphire substrate [7]. However, these reported methods involve complex and expensive processes, and long fabrication period, as well as a dry etching process, Manuscript which could result in degradation of the electrical properties of p-GaN thin layer [8].…”