Dependence of carrier concentrations on oxygen pressure for Ga-doped ZnO prepared by ion plating method

Yamamoto, Tetsuya; Sakemi, Toshiyuki; Awai, K.; Shirakata, Sho

doi:10.1016/j.tsf.2003.10.138

Cited by 72 publications

(35 citation statements)

References 14 publications

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“…However, XRD measurements indicate [8] the average grain size in these arc grown films is no larger than 40 nm. From the Hall measurements, the electron mean free path can be estimated [40] and was in the range of 10 to 30 nm for the arc-grown ICO. Thus, its likely that many electrons are crossing the grain boundaries during optical excitation, which will bring the optical mobility closer to the Hall mobility.…”

Section: Discussionmentioning

confidence: 99%

Determining the nonparabolicity factor of the CdO conduction band using indium doping and the Drude theory

Mendelsberg¹,

Zhu²,

Anders³

2012

J. Phys. D: Appl. Phys.

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Abstract. Due to their high intrinsic electron mobility, CdO-based materials are gaining interest as transparent conductive oxides. By creating model dielectric functions based on the Drude theory, accurate fits to the measured transmittance and reflectance of CdO and CdO:In thin-films were achieved without using a frequency dependent Drude damping parameter. Difference in the model between undoped and In-doped CdO showed that the Burstein-Moss shift is not the only mechanism which improves the transparency in In-doped samples. Comparing the Drude analysis with Hall measurements revealed a nonlinear relationship between the free-electron effective mass and the carrier concentration, an effect which is caused by the nonparabolicity of the CdO conduction band. Analysis of 50 CdO:In thin-films grown by pulsed filtered cathodic arc showed the nonparabolicity factor was C = (0.5 ± 0.2) eV −1 and the band-edge effective mass was (0.16 ± 0.05)me. Knowledge of the effective mass allows for optical measurements of carrier mobility, which was less than or equal to the Hall measured mobility in these films due to the large electron mean-free-path compared to the grain size.

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Section: Discussionmentioning

confidence: 99%

Determining the nonparabolicity factor of the CdO conduction band using indium doping and the Drude theory

Mendelsberg¹,

Zhu²,

Anders³

2012

J. Phys. D: Appl. Phys.

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“…Some experiments [81,82] have shown a variation in conductivity and mobility with P O 2 more indicative of the presence of interstitials or cation vacancies (which have also been shown to be present using positron annihilation spectroscopy) [83][84][85][86][87], but oxygen vacancies have been proposed to explain the intrinsic n-type conductivity [36,78,88] and persistent photoconductivity [37,76], as well as other experimental results [89][90][91][92]. Similar to SnO 2 , computational studies tend to indicate that the oxygen vacancy is deep, with the (2+/0) transition occurring at about 1 eV below the CBM [46][47][48][49][50][51][52][53].…”

Section: Introductionmentioning

confidence: 99%

Deep vs shallow nature of oxygen vacancies and consequentn-type carrier concentrations in transparent conducting oxides

Buckeridge

Catlow

Farrow

et al. 2018

Phys. Rev. Materials

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The source of n-type conductivity in undoped transparent conducting oxides has been a topic of debate for several decades. The point defect of most interest in this respect is the oxygen vacancy, but there are many conflicting reports on the shallow versus deep nature of its related electronic states. Here, using a hybrid quantum mechanical/molecular mechanical embedded cluster approach, we have computed formation and ionization energies of oxygen vacancies in three representative transparent conducting oxides: In 2 O 3 , SnO 2 , and ZnO. We find that, in all three systems, oxygen vacancies form well-localized, compact donors. We demonstrate, however, that such compactness does not preclude the possibility of these states being shallow in nature, by considering the energetic balance between the vacancy binding electrons that are in localized orbitals or in effective-mass-like diffuse orbitals. Our results show that, thermodynamically, oxygen vacancies in bulk In 2 O 3 introduce states above the conduction band minimum that contribute significantly to the observed conductivity properties of undoped samples. For ZnO and SnO 2 , the states are deep, and our calculated ionization energies agree well with thermochemical and optical experiments. Our computed equilibrium defect and carrier concentrations, however, demonstrate that these deep states may nevertheless lead to significant intrinsic n-type conductivity under reducing conditions at elevated temperatures. Our study indicates the importance of oxygen vacancies in relation to intrinsic carrier concentrations not only in In 2 O 3 , but also in SnO 2 and ZnO.

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“…We have reported high quality Ga-doped ZnO films at a high deposition rate (e.g. 170 nm/min) on large area substrate by reactive plasma deposition (RPD) method [6,7]. This method, an ion-plating method using dc arc-discharge plasma, is very attractive for the fabrication of ZnO thin films.…”

Section: Introductionmentioning

confidence: 99%

Photoconductivity of Ga doped polycrystalline ZnO films grown by reactive plasma deposition

Kishimoto

Hayashi

Hamaguchi³

et al. 2007

Physica Status Solidi (b)

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Photoconductivity and photo-absorption of polycrystalline Ga-doped ZnO (GZO) thin films with film thickness of 200 nm have evaluated compared with undoped ZnO films. The GZO and undoped ZnO thin films were deposited on alkali-free glass substrate at 200 °C by a reactive plasma deposition with DC arc discharge technique under an oxygen gas flow rate from 0 to 30 sccm. Undoped ZnO films with carrier concentration of 2.50 × 10 18 and 7.96 × 10 18 cm -3 have exciton absorption at about 3.28 eV. For these films, the photoconductivity peak is agreement with the photon-energy of exciton absorption in the optical-absorption. The optical band edge of undoped ZnO films estimated from the optical-absorption shows a shift to higher energy with increasing the carrier concentration. The increase of oxygen gas flow rate led to the resistivity change of GZO films from 2.15 × 10 -4 to 4.54 × 10 -3 Ω cm, corresponding to the carrier concentration change from 1.39 × 10 21 to 1.05 × 10 20 cm -3 . The photoconductivity of GZO film is larger than that of undoped ZnO film. The peak energy of photoconductivity spectra of GZO films are seen to little shift to higher energy with increasing the carrier concentration. The GZO film exhibited the larger photoconductivity at the wavelength, ranging widely less than 380 nm. GZO film with carrier concentration more than 1 × 10 21 cm -3 indicated much larger photoconductivity.

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Dependence of carrier concentrations on oxygen pressure for Ga-doped ZnO prepared by ion plating method

Cited by 72 publications

References 14 publications

Determining the nonparabolicity factor of the CdO conduction band using indium doping and the Drude theory

Determining the nonparabolicity factor of the CdO conduction band using indium doping and the Drude theory

Deep vs shallow nature of oxygen vacancies and consequentn-type carrier concentrations in transparent conducting oxides

Photoconductivity of Ga doped polycrystalline ZnO films grown by reactive plasma deposition

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