Effective Chemical Lift-Off for Air-Tunnel GaN on a Trapezoid-Patterned Sapphire Substrate

Min Joo Ahn, Kyu Yeon Shim, Woo Seop Jeong, Seongho Kang, Hwayoung Kim, Seunghee Cho, Dongjin Byun

Research output: Contribution to journalArticlepeer-review

Abstract

We fabricated an air-tunnel structure between a gallium nitride (GaN) layer and trapezoid-patterned sapphire substrate (TPSS) through the in situ carbonization of a photoresist layer to enable rapid chemical lift-off (CLO). A trapezoid-shaped PSS was used, which is advantageous for epitaxial growth on the upper c-plane when forming an air tunnel between the substrate and GaN layer. The upper c-plane of the TPSS was exposed during carbonization. This was followed by selective GaN epitaxial lateral overgrowth using a homemade metal organic chemical vapor deposition system. The air tunnel maintained its structure under the GaN layer, whereas the photoresist layer between the GaN layer and TPSS disappeared. The crystalline structures of GaN (0002) and (0004) were investigated using X-ray diffraction. The photoluminescence spectra of the GaN templates with and without the air tunnel showed an intense peak at 364 nm. The Raman spectroscopy results for the GaN templates with and without the air tunnel were redshifted relative to the results for free-standing GaN. The CLO process using potassium hydroxide solution neatly separated the GaN template with the air tunnel from the TPSS.

Original languageEnglish
Article number753
JournalMicromachines
Volume14
Issue number4
DOIs
Publication statusPublished - 2023 Apr

Bibliographical note

Publisher Copyright:
© 2023 by the authors.

Keywords

  • chemical lift-off
  • gallium nitride
  • trapezoid-patterned sapphire substrate

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Mechanical Engineering
  • Electrical and Electronic Engineering

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