Low temperature growth and optical properties of α-Ga2O3 deposited on sapphire by plasma enhanced atomic layer deposition

J.W. Roberts, P.R. Chalker, B. Ding, R.A. Oliver, J.T. Gibbon, L.A.H. Jones, V.R. Dhanak, L.J. Phillips, J.D. Major, F.C.-P. Massabuau

Research output: Contribution to journalArticle

Abstract

Plasma enhanced atomic layer deposition was used to deposit thin films of Ga2O3 on to c-plane sapphire substrates using triethylgallium and O2 plasma. The influence of substrate temperature and plasma processing parameters on the resultant crystallinity and optical properties of the Ga2O3 films were investigated. The deposition temperature was found to have a significant effect on the film crystallinity. At temperatures below 200°C amorphous Ga2O3 films were deposited. Between 250°C and 350°C the films became predominantly α-Ga2O3. Above 350°C the deposited films showed a mixture of α-Ga2O3 and ε-Ga2O3 phases. Plasma power and O2 flow rate were observed to have less influence over the resultant phases present in the films. However, both parameters could be tuned to alter the strain of the film. Ultraviolet transmittance measurements on the Ga2O3 films showed that the bandgaps ranges from 5.0 eV to 5.2 eV with the largest bandgap of 5.2 eV occurring for the α-Ga2O3 phase deposited at 250°C.
LanguageEnglish
Article number125254
Number of pages13
JournalJournal of Crystal Growth
Volume528
Early online date25 Sep 2019
DOIs
Publication statusE-pub ahead of print - 25 Sep 2019

Fingerprint

Atomic layer deposition
Aluminum Oxide
Growth temperature
atomic layer epitaxy
Sapphire
sapphire
Optical properties
Plasmas
optical properties
Energy gap
crystallinity
Plasma applications
Amorphous films
Substrates
Temperature
Deposits
temperature
Flow rate
transmittance
flow velocity

Keywords

  • characterization
  • crystal structure
  • crystal morphology
  • x-ray diffraction
  • atomic layer epitaxy
  • gallium compounds

Cite this

Roberts, J.W. ; Chalker, P.R. ; Ding, B. ; Oliver, R.A. ; Gibbon, J.T. ; Jones, L.A.H. ; Dhanak, V.R. ; Phillips, L.J. ; Major, J.D. ; Massabuau, F.C.-P. / Low temperature growth and optical properties of α-Ga2O3 deposited on sapphire by plasma enhanced atomic layer deposition. In: Journal of Crystal Growth. 2019 ; Vol. 528.
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Low temperature growth and optical properties of α-Ga2O3 deposited on sapphire by plasma enhanced atomic layer deposition. / Roberts, J.W.; Chalker, P.R.; Ding, B.; Oliver, R.A.; Gibbon, J.T.; Jones, L.A.H.; Dhanak, V.R.; Phillips, L.J.; Major, J.D.; Massabuau, F.C.-P.

In: Journal of Crystal Growth, Vol. 528, 125254, 15.12.2019.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Low temperature growth and optical properties of α-Ga2O3 deposited on sapphire by plasma enhanced atomic layer deposition

AU - Roberts, J.W.

AU - Chalker, P.R.

AU - Ding, B.

AU - Oliver, R.A.

AU - Gibbon, J.T.

AU - Jones, L.A.H.

AU - Dhanak, V.R.

AU - Phillips, L.J.

AU - Major, J.D.

AU - Massabuau, F.C.-P.

PY - 2019/9/25

Y1 - 2019/9/25

N2 - Plasma enhanced atomic layer deposition was used to deposit thin films of Ga2O3 on to c-plane sapphire substrates using triethylgallium and O2 plasma. The influence of substrate temperature and plasma processing parameters on the resultant crystallinity and optical properties of the Ga2O3 films were investigated. The deposition temperature was found to have a significant effect on the film crystallinity. At temperatures below 200°C amorphous Ga2O3 films were deposited. Between 250°C and 350°C the films became predominantly α-Ga2O3. Above 350°C the deposited films showed a mixture of α-Ga2O3 and ε-Ga2O3 phases. Plasma power and O2 flow rate were observed to have less influence over the resultant phases present in the films. However, both parameters could be tuned to alter the strain of the film. Ultraviolet transmittance measurements on the Ga2O3 films showed that the bandgaps ranges from 5.0 eV to 5.2 eV with the largest bandgap of 5.2 eV occurring for the α-Ga2O3 phase deposited at 250°C.

AB - Plasma enhanced atomic layer deposition was used to deposit thin films of Ga2O3 on to c-plane sapphire substrates using triethylgallium and O2 plasma. The influence of substrate temperature and plasma processing parameters on the resultant crystallinity and optical properties of the Ga2O3 films were investigated. The deposition temperature was found to have a significant effect on the film crystallinity. At temperatures below 200°C amorphous Ga2O3 films were deposited. Between 250°C and 350°C the films became predominantly α-Ga2O3. Above 350°C the deposited films showed a mixture of α-Ga2O3 and ε-Ga2O3 phases. Plasma power and O2 flow rate were observed to have less influence over the resultant phases present in the films. However, both parameters could be tuned to alter the strain of the film. Ultraviolet transmittance measurements on the Ga2O3 films showed that the bandgaps ranges from 5.0 eV to 5.2 eV with the largest bandgap of 5.2 eV occurring for the α-Ga2O3 phase deposited at 250°C.

KW - characterization

KW - crystal structure

KW - crystal morphology

KW - x-ray diffraction

KW - atomic layer epitaxy

KW - gallium compounds

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