High-efficiency InGaN-based light-emitting diodes with nanoporous GaN:Mg structure

Abstract

In this research nanoporous structures on p-type GaN:Mg and n-type GaN:Si surfaces were fabricated through a photoelectrochemical (PEC) oxidation and an oxide-removing process. The photoluminescence (PL) intensities of GaN and InGaN∕GaN multi-quantum-well (MQW) structures were enhanced by forming this nanoporous structure to increase light extraction efficiency. The PL emission peaks of an MQW active layer have a blueshift phenomenon from 465.5nm (standard) to 456.0nm (nanoporous) measured at 300K which was caused by partially releasing the compressive strain from the top GaN:Mg layers. The internal quantum efficiency could be increased by a partial strain release that induces a lower piezoelectric field in the active layer. The thermal activation energy of a nanoporous structure (85meV) is higher than the standard one (33meV) from a temperature dependent PL measurement. The internal quantum efficiency and light extraction efficiency of an InGaN∕GaN MQW active layer are significantly enhanced by this nanoporous GaN:Mg surface, and this PEC treated nanoporous structure is suitable for high-power lighting applications.

The role of mesa size in nano‐structured green AlGaInN light‐emitting diodes

“…The patterning of the LED mesa is also known to enhance the light extraction efficiency [10,11]. This should, at least partially, explain the enhanced EL brightness in the patterned area of the nano LED.…”

Analysis of Improved Efficiency of InGaN Light‐Emitting Diode With Bottom Photonic Crystal Fabricated by Anodized Aluminum Oxidxe

“…As a reference, the same layers were grown on a GaN/sapphire substrate without any pattern (sample B). Figure 1a shows a cross-sectional (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) twobeam bright-field transmission electron microscopy (TEM) image of sample A, and Figure 1b is a magnified TEM micrograph showing the region close to air holes in detail. Initially the overgrowth of GaN occurs on the area between the holes and it coalescences to form a continuous layer.…”

Photoelectrochemical roughening of p‐GaN for light extraction from GaN/InGaN light emitting diodes

“…In this work, we present a process for using PEC etching to roughen the Ga-face of p-side-up LEDs. In addition to the applications for LED roughening, this is the first demonstration of PEC etching of p-type GaN without an applied bias [8][9][10] or chopped light source [11]. Photoillumination of a p-type semiconductor results in the formation of both electrons and holes at the illuminated surface.…”