On the structural and bandgap properties of mist-CVD-grown κ-Ga2O3 post continuous temperature annealing

Yara Banda; Yanqing Jia; Seong-Ho Cho; Bambar Davaasuren; Mohamed Ben Hassine; Qingxiao Wang; Dalaver H. Anjum; Qiaoqiang Gan; Zhenqiang Ma; Si-Young Bae; Tien Khee Ng; Boon S. Ooi

doi:10.1063/5.0233281

AIP Advances (Nov 2024)

On the structural and bandgap properties of mist-CVD-grown κ-Ga2O3 post continuous temperature annealing

Yara Banda,
Yanqing Jia,
Seong-Ho Cho,
Bambar Davaasuren,
Mohamed Ben Hassine,
Qingxiao Wang,
Dalaver H. Anjum,
Qiaoqiang Gan,
Zhenqiang Ma,
Si-Young Bae,
Tien Khee Ng,
Boon S. Ooi

Affiliations

Yara Banda: Photonics Laboratory, Electrical and Computer Engineering, Division of Computer, Electrical and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
Yanqing Jia: Photonics Laboratory, Electrical and Computer Engineering, Division of Computer, Electrical and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
Seong-Ho Cho: Semiconductor Materials Center, Korea Institute of Ceramic Engineering and Technology (KICET), Jinju 52851, Republic of Korea
Bambar Davaasuren: Imaging and Characterization Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
Mohamed Ben Hassine: Imaging and Characterization Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
Qingxiao Wang: Imaging and Characterization Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
Dalaver H. Anjum: Imaging and Characterization Core Lab, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
Qiaoqiang Gan: Sustainability and Photonics Energy Research Lab, Division of Physical Science and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
Zhenqiang Ma: Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
Si-Young Bae: Semiconductor Materials Center, Korea Institute of Ceramic Engineering and Technology (KICET), Jinju 52851, Republic of Korea
Tien Khee Ng: Photonics Laboratory, Electrical and Computer Engineering, Division of Computer, Electrical and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
Boon S. Ooi: Photonics Laboratory, Electrical and Computer Engineering, Division of Computer, Electrical and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia

DOI: https://doi.org/10.1063/5.0233281
Journal volume & issue: Vol. 14, no. 11
pp. 115019 – 115019-9

Abstract

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We investigate the continuous annealing of orthorhombic κ-Ga2O3 films on AlN/c-plane sapphire templates grown by Mist Chemical Vapor Deposition (mist-CVD) using in situ high-temperature x-ray diffraction (HT-XRD). Increasing the annealing temperature from 400 to 1100 °C in both vacuum and ambient air reveals a phase transition onset at 825 °C. High-resolution transmission electron microscopy and XRD demonstrated that annealing within the stability window of 650 to 775 °C effectively improves the crystal quality of the κ-Ga2O3 thin film. Optical transmittance and low-loss electron energy loss spectroscopy (EELS) show the pristine film’s bandgaps to be 4.96 and 4.67 eV, respectively, with reduced bandgaps in annealed films due to increased defect density. EELS-derived optical joint density of states indicates that air-annealing fosters sub-bandgap radiative processes, while vacuum annealing suppresses them, qualitatively correlated with the observed photoluminescence intensity variations. The results of this comprehensive high-temperature annealing study offer crucial insight into the influence of annealing ambient conditions on the crystallographic properties of κ-Ga2O3 films and the associated evolution of extended sub-bandgap states.

Published in AIP Advances

ISSN: 2158-3226 (Online)
Publisher: AIP Publishing LLC
Country of publisher: United States
LCC subjects: Science: Physics
Website: http://aipadvances.aip.org/

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