Evolution and growth of ZnO thin films on GaN(0001) epilayers via metalorganic vapor phase epitaxy

Smith, Thor L.; Mecouch, W. J.; Miraglia, P.Q.; Roskowski, A. M.; Hartlieb, P. J.; Davis, R. F.

doi:10.1016/s0022-0248(03)01469-6

Cited by 22 publications

(17 citation statements)

References 32 publications

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“…Bulk gap widths and densities of states (DOS) have been scrutinized by first principles simulations 10,11 and we have recently disentangled the effects of band narrowing and of electrostatics in the modifications of quasi particle, absorption and electron energy loss spectra 12 . Beyond bulk properties, the possibility of tuning electronic and optical properties through a reduction of dimensionality has fostered advances in the fabrication and structural characterization of ZnO nanostructures [13][14][15][16][17][18][19] and thin films on various substrates [20][21][22][23][24][25][26][27][28][29][30] , with a range of techniques and under a variety of experimental conditions. In particular in ultra-thin films, theoretical and experimental works indicate important variations of the atomic structure as a function of thickness [31][32][33][34] .…”

Section: Introductionmentioning

confidence: 99%

Confinement effects in ultrathin ZnO polymorph films: Electronic and optical properties

2016

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Relying on generalized-gradient and hybrid first-principles simulations, this work provides a complete characterization of the electronic properties of ZnO ultra-thin films, cut along the BodyCentered-Tetragonal(010), Cubane(100), h-BN(0001), Zinc-Blende(110), Wurtzite (1010) and (0001) orientations. The characteristics of the local densities of states are analyzed in terms of the reduction of the Madelung potential on under-coordinated atoms and surface states/resonances appearing at the top of the VB and bottom of the CB. The gap width in the films is found to be larger than in the corresponding bulks, which is assigned to quantum confinement effects. The components of the high frequency dielectric constant are determined and the absorption spectra of the films are computed. They display specific features just above the absorption threshold due to transitions from or to the surface resonances. This study provides a first understanding of finite size effects on the electronic properties of ZnO thin films and a benchmark which is expected to foster experimental characterization of ultra-thin films via spectroscopic techniques.

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Section: Introductionmentioning

confidence: 99%

Confinement effects in ultrathin ZnO polymorph films: Electronic and optical properties

2016

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“…2 %) with room temperature lattice parameters of a Z = 0.325 nm, c Z = 0.521 nm and a G = 0.319 nm, c G = 0.519 nm, one would expect that ZnO epitaxial thin films on GaN would produce superior properties. Epitaxial ZnO films have been grown on GaN substrates using different vapor-phase methods including metal-organic chemical vapor deposition (MOCVD), [18,19] metal-organic vapor-phase epitaxy, [20][21][22][23][24] pulsed laser deposition (PLD), [25][26][27] and molecular beam epitaxy (MBE). [28][29][30][31] Recently it was shown that lateral epitaxial overgrowth (LEO) of ZnO films on (111) spinel substrates could be accomplished in water at 90°C.…”

Section: Introductionmentioning

confidence: 99%

Growth of Heteroepitaxial ZnO Thin Films on GaN‐Buffered Al₂O₃ (0001) Substrates by Low‐Temperature Hydrothermal Synthesis at 90 °C

Kim

Andeen

et al. 2007

Adv Funct Materials

104

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Heteroepitaxial ZnO films are successfully grown on nondoped GaN‐buffered Al2O3 (0001) substrates in water at 90 °C using a two‐step process. In the first step, a discontinuous ZnO thin film (ca. 200 nm in thickness) consisting of hexagonal ZnO crystallites is grown in a solution containing Zn(NO3)·6 H2O and NH4NO3 at ca. pH 7.5 for 24 h. In the second step, a dense and continuous ZnO film (ca. 2.5 μm) is grown on the first ZnO thin film in a solution containing Zn(NO3)·6 H2O and sodium citrate at ca. pH 10.9 for 8 h. Scanning electron microscopy, X‐ray diffraction, UV‐vis absorption spectroscopy, photoluminescence spectroscopy, and Hall‐effect measurement are used to investigate the structural, optical, and electrical properties of the ZnO films. X‐ray diffraction analysis shows that ZnO is a monocrystalline wurtzite structure with an epitaxial orientation relationship of (0001)[11$ \bar 2 $0]ZnO∥(0001)[11$ \bar 2 $0]GaN. Optical transmission spectroscopy of the two‐step grown ZnO film shows a bandgap energy of 3.26 eV at room temperature. A room‐temperature photoluminescence spectrum of the ZnO film reveals only a main peak at ca. 380 nm without any significant defect‐related deep‐level emissions. The electrical property of ZnO film showed n‐type behavior with a carrier concentration of 3.5 × 1018 cm–3 and a mobility of 10.3 cm2 V–1 s–1.

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“…There was no visual indication of an intermediate oxide or amorphous phase at the interface. However, x-ray photoelectron spectroscopy of ZnO films grown for 2 min on similar and similarly in-situ pretreated substrates at 450°C in this research 40 showed the presence of the O 1s and the position of the Ga 3d core levels to be consistent with the Ga-O bond in Ga 2 O 3 , which was indicative of a very thin oxide with at least partial coverage of the GaN surface. It is believed that the same interface chemistry pertains for the films grown in this study and that it is the likely reason for the irregularities noted above in the vertical stacking of the (0001) planes.…”

Section: Resultsmentioning

confidence: 49%

“…Prior research in this laboratory concerned with the deposition of ZnO on similar substrates at 450°C in tandem with x-ray photoelectron spectroscopy revealed that these films grew via Stranski-Krastanov mode. 40 In this mode, the initial growth of a coherent film occurs via a layer-by-layer mechanism and is subsequently followed by the initiation of island growth. The surface and interfacial energies of and between the film and substrate and the stress within the growing film determine the prevailing growth mode.…”

Section: Methodsmentioning

confidence: 99%

Growth and characterization of ZnO thin films on GaN epilayers

Smith

Mclean

Smith

et al. 2004

Journal of Elec Materi

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Dense ZnO(0001) films formed at 500°C via coalescence of islands grown via metalorganic vapor phase epitaxy (MOVPE) either on GaN/AlN/SiC(0001) substrates or on initial, coherent ZnO layers. Conical crystallites formed due to thermal expansion-induced stresses between the ZnO and the substrate. Interfaces between the ZnO films on GaN epilayers exposed either simultaneously to diethylzinc and oxygen or only to diethylzinc at the initiation of growth were sharp and epitaxial. Interfaces formed after the exposure of the GaN to O 2 were less coherent, though an interfacial oxide was not observed by cross-sectional transmission electron microscopy (TEM). Threading dislocations and stacking faults were observed in all films.

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Evolution and growth of ZnO thin films on GaN(0001) epilayers via metalorganic vapor phase epitaxy

Cited by 22 publications

References 32 publications

Confinement effects in ultrathin ZnO polymorph films: Electronic and optical properties

Confinement effects in ultrathin ZnO polymorph films: Electronic and optical properties

Growth of Heteroepitaxial ZnO Thin Films on GaN‐Buffered Al₂O₃ (0001) Substrates by Low‐Temperature Hydrothermal Synthesis at 90 °C

Growth and characterization of ZnO thin films on GaN epilayers

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Evolution and growth of ZnO thin films on GaN(0001) epilayers via metalorganic vapor phase epitaxy

Cited by 22 publications

References 32 publications

Confinement effects in ultrathin ZnO polymorph films: Electronic and optical properties

Confinement effects in ultrathin ZnO polymorph films: Electronic and optical properties

Growth of Heteroepitaxial ZnO Thin Films on GaN‐Buffered Al2O3 (0001) Substrates by Low‐Temperature Hydrothermal Synthesis at 90 °C

Growth and characterization of ZnO thin films on GaN epilayers

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Growth of Heteroepitaxial ZnO Thin Films on GaN‐Buffered Al₂O₃ (0001) Substrates by Low‐Temperature Hydrothermal Synthesis at 90 °C