β‐Gallium Oxide as Oxygen Gas Sensors at a High Temperature

Bartic, Marilena; Baban, C.; Suzuki, Hisao; Ogita, Masami; Isai, Masaaki

doi:10.1111/j.1551-2916.2007.01842.x

Cited by 119 publications

(72 citation statements)

References 21 publications

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“…5 However, while Si-doping can increase the conductivity of Ga 2 O 3 , this does not explain its dependence on pðO 2 ), which is convincingly demonstrated for Ga 2 O 3 in a gas sensing device. Bartic et al 6 demonstrated a few percent change in the conductivity of a single crystal device at 1000 C due to changes in pðO 2 ); for the single crystal sensor, the active region was found to be confined to a narrow region near the surface.…”

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confidence: 98%

Band bending and surface defects in β-Ga2O3

Lovejoy

Chen

Zheng

et al. 2012

Applied Physics Letters

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Surface band bending and surface defects on the UV-transparent conducting oxide β-Ga2O3 (100) are studied with hard x-ray photoemission spectroscopy and scanning tunneling microscopy. Highly doped β-Ga2O3 shows flat bands near the surface, while the bands on nominally undoped (but still n-type), air-cleaved β-Ga2O3 are bent upwards by ≳0.5 eV. Negatively charged surface defects are observed on vacuum annealed β-Ga2O3, which also shows upward band bending. Density functional calculations show oxygen vacancies are not likely to be ionized in the bulk, but could be activated by surface band bending. The large band bending may also hinder formation of ohmic contacts.

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confidence: 98%

Band bending and surface defects in β-Ga2O3

Lovejoy

Chen

Zheng

et al. 2012

Applied Physics Letters

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“…25) due to an oxygen deficit occurring at these temperatures, and as a result it has been investigated as the active material for high temperature oxygen sensors. 26,27 Furthermore, the large bandgap of Ga 2 O 3 ($4.9 eV (Refs. 25, 28, and 29)), only second in magnitude to diamond among known semiconductors, combined with its extremely high electric field strengthhigher than GaN and SiC-makes this binary oxide very interesting for a variety of optoelectronic applications.…”

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confidence: 99%

High electron mobility thin-film transistors based on Ga2O3 grown by atmospheric ultrasonic spray pyrolysis at low temperatures

Thomas

Adamopoulos

Lin

et al. 2014

Applied Physics Letters

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We report on thin-film transistors based on Ga2O3 films grown by ultrasonic spray pyrolysis in ambient atmosphere at 400–450 °C. The elemental, electronic, optical, morphological, structural, and electrical properties of the films and devices were investigated using a range of complementary characterisation techniques, whilst the effects of post deposition annealing at higher temperature (700 °C) were also investigated. Both as-grown and post-deposition annealed Ga2O3 films are found to be slightly oxygen deficient, exceptionally smooth and exhibit a wide energy bandgap of ∼4.9 eV. Transistors based on as-deposited Ga2O3 films show n-type conductivity with the maximum electron mobility of ∼2 cm2/V s.

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“…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].…”

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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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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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β‐Gallium Oxide as Oxygen Gas Sensors at a High Temperature

Cited by 119 publications

References 21 publications

Band bending and surface defects in β-Ga2O3

Band bending and surface defects in β-Ga2O3

High electron mobility thin-film transistors based on Ga2O3 grown by atmospheric ultrasonic spray pyrolysis at low temperatures

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

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