New luminescence band due to nitrogen impurities in gallium oxide powders

Cho, Sungryong; Lee, Jongwon; Park, In-Yong; Kim, Seontai

doi:10.1016/s0167-577x(02)00914-x

Cited by 14 publications

(10 citation statements)

References 9 publications

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“…The structure with lowest energy we found exhibiting one octahedral and one tetrahedral vacancy in the cation sublattice has an excess energy of about 0.3 eV (per 54 atoms). Due to the presence of two defect sites in the unit cell, the models of Ga 22 The above results indicate that a spinel-type gallium oxynitride phase has a positive enthalpy of formation. Therefore, if we base our argument on enthalpy, which is correct for zero temperature, it looks impossible to synthesize the ternary compound using equilibrium methods.…”

Section: Defective Spinel-type Structuresmentioning

confidence: 86%

“…It is a wide-gap, n-type semiconductor with an optical band gap of 4.9 eV [18]. bGa 2 O 3 has applications as a luminescent phosphor [19], as an oxygen sensor [3,20], as a deep-ultraviolet transparent oxide [21], and in different high temperature electronic applications [22]. bGa 2 O 3 exhibits a slight oxygen-deficiency that is generally interpreted in terms of oxygen vacancies [23,24].…”

Section: Introductionmentioning

confidence: 99%

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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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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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Section: Defective Spinel-type Structuresmentioning

confidence: 86%

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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“…5 b-Ga 2 O 3 is a direct semiconductor with a band gap of 4.9 eV and is used as sensor material and in different high-temperature electronics applications. 6 A common way of synthesising a-GaN is the ammonolysis of b-Ga 2 O 3 :…”

Section: Introductionmentioning

confidence: 99%

An in situ XAS investigation of the kinetics of the ammonolysis of Ga2O3 and the oxidation of GaN

Brendt

Samuelis

Weirich

et al. 2009

Phys. Chem. Chem. Phys.

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The ammonolysis of beta-Ga(2)O(3) to alpha-GaN and the oxidation of alpha-GaN to beta-Ga(2)O(3) have been studied by means of in situ X-ray absorption spectroscopy (XAS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). In situ X-ray absorption measurements on polycrystalline powder particles on the gallium K-edge during both reactions give detailed information about the reaction kinetics. We were able to extract this kinetics by fitting linear combinations of beta-Ga(2)O(3) and alpha-GaN spectra only. The kinetics of the ammonolysis can be described well by an extended Johnson-Mehl-Avrami-Kolmogorow model, while the oxidation kinetics can be modelled by a shrinking core model. Investigations by means of TEM and SEM support the assumptions in both models. Our experimental results and the models are discussed in terms of the reaction energetics and the reaction mechanisms.

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“…The preparation of bulk powders [3], thin films [4,5] and single crystals [6] of b-Ga 2 O 3 by different thechniques are reported. Due to high band gap ($4.8 eV) [7] it has applicaton as a deep UV transparent conducting oxide [8] antireflection [9] and passivation [10] coatings.…”

Section: Introductionmentioning

confidence: 99%

“…Due to high band gap ($4.8 eV) [7] it has applicaton as a deep UV transparent conducting oxide [8] antireflection [9] and passivation [10] coatings. Because of interesting luminescence properties [3] it has a useful application as phosphors [11,12]. Thermally and chemically stable b-Ga 2 O 3 behaves as an n-type semiconductor [13] and has application as sensors [13][14][15].…”

Section: Introductionmentioning

confidence: 99%