High-electron-mobility ZnO epilayers grown by plasma-assisted molecular beam epitaxy

This version is available at https://strathprints.strath.ac.uk/54019/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. Transmission electron microscopy reveals that these effects are caused by phase separation leading to the formation of a vertically ordered rock salt/wurtzite heterostructures. To explain these observations we suggest a phase separation epitaxy model that considers this process being initiated by the formation of a cubic (Mg,Zn)Al 2 O 4 spinel layer at the interface to the sapphire substrate, acting as a planar seed for the epitaxial precipitation of rock salt-type Mg x Zn 1-x O. The equilibrium fraction x of magnesium in the resulting wurtzite (rock salt) layers is approximately 0.15 (0.85), independent of the MgO content of the as-grown layer and determined by the annealing temperature. This model is confirmed by photoluminescence analysis of the resulting layer systems after different annealing temperatures. In addition we show that the thermal annealing process 2 results in a significant reduction in the density of edge-and screw-type dislocations, providing the possibility to fabricate high quality templates for quasi-homoepitaxial growth.3

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“…Consistent with earlier reports a higher density of edge-type than screw-type dislocations is observed [8,21,31,32] [7,[15][16][17][18].…”

Section: Comparison Tosupporting

confidence: 92%

Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in MgxZn1−xO

Gries

Wassner

Vogel

et al. 2015

Journal of Applied Physics

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“…Figure 11 shows the relationship between Hall mobility and carrier concentration for ZnO films on Al 2 O 3 substrates. Both the mobility and carrier concentration in this work were comparable to those for films grown by MBE or PLD [16][17][18][19], which have not been realized by using conventional MOCVD [20,21].…”

Section: Effect Of Thicknesssupporting

confidence: 66%

Improved transport properties for ZnO films on Al₂O₃(11$\bar2$0) by MOCVD

Hiragino

Furubayashi

Moriyama

et al. 2014

Phys. Status Solidi C

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ZnO films on Al2O3 (112$\bar2$0) with excellent transport properties were grown using metalorganic chemical vapor deposition (MOCVD) with a high speed rotating disk and a separated showerhead. Diisopropylzinc and tert ‐butanol were used as Zn and O precursors, respectively. Hall‐effect measurements revealed that the ZnO films in this work showed a high mobility of 140 cm2/Vs and a low carrier concentration of 1.5×1017 cm–3, both of which are comparable to those grown by molecular beam epitaxy or pulsed laser deposition. This report should open a way to the mass production of single crystalline ZnO films which should be usable for optoelectronic devices. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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“…[12,22] Previous studies of MBE-grown epitaxial ZnO show a higher concentration of edge dislocations relative to screw dislocations. [22][23][24][25] Bright-field TEM images from the [112 0] zone axis, tilted to g = 0002 for screw dislocations, and g = 101 0 for edge dislocations, provide conditions to image each dislocation type independently. Mixed dislocations will appear in both images.…”

Section: Full Papermentioning

confidence: 99%

Lateral Epitaxial Overgrowth of ZnO in Water at 90 °C

et al. 2006

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Lateral epitaxial overgrowth (LEO) of ZnO has been demonstrated in water at 90 °C. The process starts with hydrothermal epitaxial growth of ZnO(0001) on MgAl2O4(111), followed by channel stamping of photoresist to define “growth windows”. LEO films grow in zinc‐precursor solutions at pH 10.9; sodium citrate addition controls out‐of‐plane growth. Transmission electron microscopy indicates threading dislocation reductions from ∼ 2 × 1010 to < 2 × 108 cm–2 from the window to the wing regions. Microphotoluminescence and Hall‐effect measurements indicate improved material quality. Wing tilt was observed. Double LEO demonstrates the possibility of complete dislocation reduction.

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High-electron-mobility ZnO epilayers grown by plasma-assisted molecular beam epitaxy

Cited by 81 publications

References 30 publications

Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in MgxZn1−xO

Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in MgxZn1−xO

Improved transport properties for ZnO films on Al₂O₃(11$\bar2$0) by MOCVD

Lateral Epitaxial Overgrowth of ZnO in Water at 90 °C

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High-electron-mobility ZnO epilayers grown by plasma-assisted molecular beam epitaxy

Cited by 81 publications

References 30 publications

Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in MgxZn1−xO

Self-assembly of ordered wurtzite/rock salt heterostructures—A new view on phase separation in MgxZn1−xO

Improved transport properties for ZnO films on Al2O3(11$\bar2$0) by MOCVD

Lateral Epitaxial Overgrowth of ZnO in Water at 90 °C

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Improved transport properties for ZnO films on Al₂O₃(11$\bar2$0) by MOCVD