Electrical properties of β-Ga2O3 single crystals

In situ XAS Nucleation Non-stoichiometry Amorphous oxide Insulator-metal transition a b s t r a c t Within the ternary system Ga-O-N we performed experimental and theoretical investigations on the thermodynamics, structure and kinetics of new stable and metastable compounds.We studied the ammonolysis of b-Ga 2 O 3 at elevated temperatures by means of ex situ X-ray diffraction, ex situ neutron diffraction, and in situ X-ray absorption spectroscopy (XAS). From total diffraction pattern refinement with the Rietveld method we analyzed the anionic occupancy factors and the lattice parameters of b-Ga 2 O 3 during the reaction. Within the detection limits of these methods, we can rule out the existence of a crystalline oxynitride phase that is not derived from wurtzite-type GaN. The nitrogen solubility in b-Ga 2 O 3 was found to be below the detection limit of about 2-3 at.% in the anionic sublattice. The kinetics of the ammonolysis of b-Ga 2 O 3 to a-GaN and of the oxidation of a-GaN to b-Ga 2 O 3 was studied by means of in situ X-ray absorption spectroscopy. In both cases the reaction kinetics could be described well by fitting linear combinations of b-Ga 2 O 3 and a-GaN spectra only, excluding that other crystalline or amorphous phases appear during these reactions. The kinetics of the ammonolysis can be described well by an extended Johnson-Mehl-Avrami-Kolmogorow model with nucleation and growth of GaN nuclei, while the oxidation kinetics can be modeled by a shrinking core model where Ga 2 O 3 grows as a layer. Investigations by means of TEM and SEM support the assumptions in both models.To investigate the structure and energetics of spinel-type gallium oxynitrides (g-galons) we performed first-principles calculations using density-functional theory. In addition to the ideal cubic g-Ga 3 O 3 N we studied gallium deficient g-galons within the Constant-Anion-Model.In highly non-stoichiometric, amorphous gallium oxide of approximate composition GaO 1.2 we found at a temperature around 670 K an insulator-metal transition, with a conductivity jump of seven orders of magnitude. We demonstrate through experimental studies and density-functional theory calculations that the conductivity jump takes place at a critical gallium concentration and is induced by crystallization of stoichiometric b-Ga 2 O 3 within the metastable oxide matrix. By doping with nitrogen the critical temperature and the conductivity in the highly conducting state can be tuned.

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“…The structure, which is shown in Fig. 15 5 , and {Ga}O 6 . In addition there are three {Ga}O 4 and five {Ga}NO 3 tetrahedra.…”

Section: Defective Spinel-type Structuresmentioning

confidence: 99%

“…Recent developments have shown increased interest in gallium oxide and gallium nitride compounds as base materials for (opto-) electronic components such as light emitting diodes or sensors [1][2][3][4][5]. Both compounds belong to the system Ga-O-N the phase diagram of which is shown schematically as a Gibbs triangle in Fig.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics, structure and kinetics in the system Ga–O–N

Martin

Dronskowski

Janek

et al. 2009

Progress in Solid State Chemistry

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“…Recent developments have shown increased interest in gallium oxide and gallium nitride compounds as base materials for (opto-) electronic components such as light emitting diodes or sensors [1][2][3][4][5]. While there have been extensive efforts in researching the binary compounds b-Ga 2 O 3 and GaN, there is only a smaller number of reports on gallium oxynitrides, that are intermediate compounds in the pseudo-binary system GaN-Ga 2 O 3 .…”

Section: Introductionmentioning

confidence: 99%

On the ammonolysis of Ga2O3: An XRD, neutron diffraction and XAS investigation of the oxygen-rich part of the system Ga2O3–GaN

Roehrens

Brendt

Samuelis

et al. 2010

Journal of Solid State Chemistry

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GaN Ammonolysis Oxynitrides Nitrogen solubility a b s t r a c tWe investigated the ammonolysis of b-Ga 2 O 3 at elevated temperatures by means of ex situ X-ray diffraction, ex situ neutron diffraction and in situ X-ray absorption spectroscopy. Within the detection limits of these methods, we can rule out the existence of a crystalline or amorphous oxynitride phase that is not derived from wurtzite-type GaN. No evidence for a b-Ga 2 O 3 related oxynitride phase was found, and the nitrogen solubility in b-Ga 2 O 3 was found to be below the detection limit of about 2-3 at% in the anionic sublattice. These findings were obtained by monitoring the anionic occupancy factors and the lattice parameters of the b-Ga 2 O 3 phase obtained from total diffraction pattern refinement with the Rietveld method and by linear combination fitting of the X-ray absorption spectra that were recorded during the ammonolysis.

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“…Another peak at 417.8 nm has a blue shift to a shorter wavelength, resulting from the quantum size effect associated with the nanorods [11]. The peak position in the blue emission region has been suggested to depend on the dimension of nanomaterials, as well as the processing conditions [12,13]. Gallium oxide nanorods may have potential application in active devices such as blue emitters due to their possibilities of strong emission [14].…”

Section: Resultsmentioning

confidence: 99%

Growth of β-Ga₂O₃Nanorods and Photoluminescence Properties

et al. 2007

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β-Ga 2 O 3 nanorods were successfully fabricated through annealing Ga2O3/Mo films deposited on the Si (111) substrate by radio frequency magnetron sputtering technique. The morphology and structure of the as-synthesized nanorods were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and energy dispersive X-rays spectroscopy. The results show that the formed nanorods are single-crystalline Ga 2 O 3 with monoclinic structure. The diameters of nanorods are 200 nm and lengths typically up to several micrometers. A photoluminescence spectrum at room temperature under excitation at 325 nm exhibits two strong blue-light peaks located at about 413.0 nm and 437.5 nm, attributed to the recombination of bound electron-hole exciton in β-Ga 2 O 3 single crystal. The growth process of the β-Ga 2 O 3 nanorods is probably dominated by conventional vapor-solid mechanism.

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Electrical properties of β-Ga2O3 single crystals

Cited by 114 publications

References 6 publications

Thermodynamics, structure and kinetics in the system Ga–O–N

Thermodynamics, structure and kinetics in the system Ga–O–N

On the ammonolysis of Ga2O3: An XRD, neutron diffraction and XAS investigation of the oxygen-rich part of the system Ga2O3–GaN

Growth of β-Ga₂O₃Nanorods and Photoluminescence Properties

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Electrical properties of β-Ga2O3 single crystals

Cited by 114 publications

References 6 publications

Thermodynamics, structure and kinetics in the system Ga–O–N

Thermodynamics, structure and kinetics in the system Ga–O–N

On the ammonolysis of Ga2O3: An XRD, neutron diffraction and XAS investigation of the oxygen-rich part of the system Ga2O3–GaN

Growth of β-Ga2O3Nanorods and Photoluminescence Properties

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Growth of β-Ga₂O₃Nanorods and Photoluminescence Properties