A resonant‐cavity blue–violet light‐emitting diode with conductive nanoporous distributed Bragg reflector

Abstract

While III‐Nitride micro‐cavity light emitters are of great interest, electrically conductive and optically highly reflective distributed Bragg mirrors remain a major challenge. In this paper, we demonstrate a blue–violet resonant‐cavity light‐emitting diode (RC‐LED) with a novel conductive nanoporous (NP)‐GaN/GaN DBR as the bottom mirror. The NP‐DBR is converted from an all‐GaN epitaxial structure with modulated doping profile, and formed by using a conductivity‐selective anodic electro‐chemical etching process. The NP‐GaN material has a tunable index of refraction and maintains its electrical conductivity. The benefits of such NP‐DBR RC‐LED include a more efficient quasi‐vertical current injection scheme benefited from the conductive NP‐DBR, and a manufacturable fabrication process, which makes NP‐DBR a unique opportunity for the commercialization of GaN‐based vertical‐cavity surface emitters.

Distributed Bragg Reflectors for GaN-Based Vertical-Cavity Surface-Emitting Lasers

“…These properties combined present a unique opportunity to build GaN VCSELs. High-reflectance NP GaN DBR mirrors [117][118][119][120][121][122], optically pumped VCSELs [117,118], and resonant-cavity LEDs (RC-LEDs) [123,124] have been demonstrated by many groups in recently years. The ultimate viability of NP GaN DBRs will be determined by their long-term stability against thermal and electrical stresses.…”

Performance improvement of ultraviolet-A multiple quantum wells using a vertical oriented nanoporous GaN underlayer

“…Nanoporous GaN also allows the tuning of the effective index of refraction for photonic devices by manipulating the porosity [4][5][6]. It is a new direction for photonic devices such as nanoporous layer embedded resonant-cavity light emitting diodes (RC-LEDs) [7], which have higher intensity and higher spectral purity compared to conventional LEDs [8].…”

Light-output enhancement of InGaN light emitting diodes regrown on nanoporous distributed Bragg reflector substrates

“…Another strategy for increasing the extraction efficiency is the inclusion of distributed Bragg reflectors (DBRs) underneath the active layers of the device. A DBR consists of layers of alternating high and low refractive index material that can be defined during epitaxial wafer growth, and may therefore be inserted at a precise depth in the wafer, enabling application to devices such as resonant-cavity LEDs 10) . Alloys of AlGaN 11,12) or AlInN 13,14) may be used as the low-index material, with GaN or a different composition of AlGaN used as the high-index material.…”

“…A DBR consists of layers of alternating high and low refractive index material that can be defined during epitaxial wafer growth, and may therefore be inserted at a precise depth in the wafer, enabling application to devices such as resonant-cavity LEDs. 10) Alloys of AlGaN 11,12) or AlInN 13,14) may be used as the low-index material, with GaN or a different composition of AlGaN used as the high-index material. However, there will be a lattice mismatch between compositions of Al x Ga 1−x N that will increase as the refractive index contrast increases, and this means that the achievable refractive index contrast is low.…”