Zinc Sulphide Overlayer Two-Dimensional Photonic Crystal for Enhanced Extraction of Light from a Micro Cavity Light-Emitting Diode

TL;DR

This paper demonstrates that a ZnS 2D photonic crystal on a micro cavity LED surface effectively redirects guided light, enhancing light extraction without damaging the device surface, thus improving LED efficiency.

Contribution

The study introduces a ZnS 2D photonic crystal overlay on a micro cavity LED, avoiding etching damage and improving light extraction through diffraction of guided modes.

Findings

Enhanced light extraction efficiency observed.

ZnS photonic crystal effectively redirects guided light.

No damage to the contact layer during fabrication.

Abstract

A two-dimensional (2D) ZnS photonic crystal was deposited on the surface of a one-dimensional (1D) III-nitride micro cavity light-emitting diode (LED), to intermix the light extraction features of both structures (1D+2D). The deposition of an ideal micro-cavity optical thickness of lambda/2 is impractical for III-nitride LEDs, and in realistic multi-mode devices a large fraction of the light is lost to internal refraction as guided light. Therefore, a 2D photonic crystal on the surface of the LED was used to diffract and thus redirect this guided light out of the semiconductor over several hundred microns. Additionally, the employment of a post-epitaxy ZnS 2D photonic crystal avoided the typical etching into the GaN:Mg contact layer, a procedure which can cause damage to the near surface.