Optical Properties of nanoporous GaN structure transformed from GaN epitaxial layer

Abstract

A Si-heavy doped GaN:Si epitaxial layer is transformed into a directional nanopipe GaN layer though a laser scribing process and a selectively electrochemical (EC) etching process. InGaN light-emitting diodes (LED) with the treated nanopipe GaN layer had high light extraction efficiency. Directional nanopipe structure is perpendicular to the laser scribing line and guided by an external bias electric field. Wide etching width (560µm) and high lateral etching rate (9.3µm/min) were achieved for forming the nanopipe GaN structure. InGaN LED structure with embedded nanopipe GaN layer can enhance the external quantum efficiency through one-step epitaxial growth process and the selectively EC etching process. Birefringence optical property and low effective refractive index are observed in the directional nanopipe GaN layer. And, the InGaN LED structure with an embedded 1/4λ-stack nanoporous-GaN/undoped-GaN distributed Bragg reflectors structure had also been demonstrated.