Mesoporous GaN for Photonic Engineering-Highly Reflective GaN Mirrors as an Example

Cheng Zhang, Sung Hyun Park, Danti Chen, Da Wei Lin, Wen Xiong, Hao-Chung Kuo, Chia Feng Lin, Hui Cao, Jung Han*

*Corresponding author for this work

Research output: Contribution to journalArticle

66 Scopus citations

Abstract

A porous medium is a special type of material where voids are created in a solid medium. The introduction of pores into a bulk solid can profoundly affect its physical properties and enable interesting mechanisms. In this paper, we report the use of mesoporous GaN to address a long-standing challenge in GaN devices: tuning the optical index in epitaxial structures without compromising the structural and electrical properties. By controlling the doping and electrochemical etching bias, we are able to control the pore morphology from macro- to meso- and microporous. The meso- and microporous GaN can be considered a new form of GaN with unprecedented optical index tunability. We examine the scattering loss in a porous medium quantitatively using numerical, semiempirical, and experimental methods. It is established that the optical loss due to scattering is well within the acceptable range. While being perfectly lattice-matched to GaN, the porous GaN layers are found to be electrically highly conductive. As an example of optical engineering, we demonstrate record high reflectances (R > 99.5%) from epitaxial mesoporous GaN mirrors that can be controllably fabricated, a result that is bound to impact GaN opto and photonic technologies.

Original languageEnglish
Pages (from-to)980-986
Number of pages7
JournalACS Photonics
Volume2
Issue number7
DOIs
StatePublished - 15 Jul 2015

Keywords

  • distributed Bragg reflector
  • electrochemical etching
  • gallium nitride
  • mesoporous
  • photonic engineering
  • vertical-cavity surface-emitting laser

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