Persistent n-type photoconductivity in p-type ZnO

Claflin, B.; Look, David C.; Park, Seong-Ju; Cantwell, G.

doi:10.1016/j.jcrysgro.2005.10.035

Cited by 113 publications

(72 citation statements)

References 50 publications

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“…The decay of PPC in this sample while in vacuum was very slow, similar to previous observations 11,13 in other ZnO samples. Temperature dependences of n and H after the PPC was allowed to relax fully and the sample was exposed to air are shown in Figs.…”

Section: Resultssupporting

confidence: 91%

“…[4][5][6][7] Changes in the electrical conductivity by several orders of magnitude have been attributed 3,[8][9][10][11] to surface accumulation or depletion layers produced by adsorbed gases such as H or O and can be enhanced 12,13 by UV light irradiation. More recent work [14][15][16][17] has demonstrated that the origin of the surface conductive layer in ZnO is more complicated than the simple adsorption model and has focused on the development of quantitative tools to analyze the surface donors and acceptors.…”

Section: Introductionmentioning

confidence: 99%

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UV light-induced changes to the surface conduction in hydrothermal ZnO

Claflin¹

2009

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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High quality, bulk ZnO crystals grown by Tokyo Denpa using the hydrothermal process typically exhibit a room temperature carrier concentration in the 1013–1014 cm−3 range and a low mobility, conductive surface layer, observed at low temperature, with a sheet concentration on the order of 1012–1013 cm−2. In the sample discussed here, bulk conduction is controlled by two donor levels at 50 and 400 meV with concentrations of 1.2×1016 and 1.5×1016 cm−3, respectively. Temperature-dependent photo-Hall-effect measurements, using blue/UV light, in vacuum show an increase in the surface sheet carrier density to more than 1×1013 cm−2 at low to intermediate temperatures while the two bulk donors continue to dominate the high temperature behavior, up to 400 K. Long-lived persistent photoconductivity (PPC) is observed when the sample is returned to the dark. When the PPC is allowed to fully relax and the sample is exposed to air, there is surprisingly no longer any surface conduction at low temperature, while the two bulk donors remain unaffected. In this state, the 50 meV bulk donor level is observed to control the conduction over five orders of magnitude, down to a carrier concentration of 3.0×108 cm−3. This corresponds to an upper limit for the surface sheet carrier density of 1.6×107 cm−2. This is the lowest surface concentration we have ever observed in any ZnO sample and demonstrates that blue/UV light irradiation, in vacuum, at moderate temperatures is very effective at cleaning the surface. A subsequent 30 min anneal at 600 °C in forming gas (5% H2 in N2) increases the carrier concentration by almost two orders of magnitude. The forming gas anneal produces no changes in the concentrations of the 50 and 400 meV bulk donor levels and no new bulk donors are observed. However, the bulk acceptor concentration decreases from 2×1016 to 1.2×1016 cm−3, most likely as a result of passivation by hydrogen.

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Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

UV light-induced changes to the surface conduction in hydrothermal ZnO

Claflin¹

2009

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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“…11 Actually, unlike the case of bare ZnO samples, the mesa n − p diodes with Ni/Al Ohmic contacts on top of the ZnO:Al layer do not show serious PPC at room temperature. Typical I − V characteristics of the n − p diodes, measured at temperatures from 200 to 400 K, are shown in Fig.…”

Section: Resultsmentioning

confidence: 94%

Electron and hole traps in N-doped ZnO grown on p-type Si by metalorganic chemical vapor deposition

Fang

Claflin

Kerr

et al. 2007

Journal of Applied Physics

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Electron and hole traps in N-doped ZnO were investigated using a structure of n + -ZnO:Al/ i-ZnO/ ZnO:N grown on a p-Si substrate by metalorganic chemical vapor deposition ͑for growth of the ZnO:N layer͒ and sputtering deposition ͑for growth of the i-ZnO and n + -ZnO:Al layers͒. Current-voltage and capacitance-voltage characteristics measured at temperatures from 200 to 400 K show that the structure is an abrupt n + − p diode with very low leakage currents. By using deep level transient spectroscopy, two hole traps, H3 ͑0.35 eV͒ and H4 ͑0.48 eV͒, are found in the p-Si substrate, while one electron trap E3 ͑0.29 eV͒ and one hole trap H5 ͑0.9 eV͒ are observed in the thin ZnO:N layer. Similarities to traps reported in the literature are discussed.

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“…Undoped ZnO shows n-type conductivity due to the existence of native defects such as oxygen vacancy, zinc interstitials, and hydrogen interstitials in the ZnO lattice [9][10][11]. Unfortunately, the conductivity of undoped ZnO is thermally unstable.…”

Section: Introductionmentioning

confidence: 99%

“…Unfortunately, the conductivity of undoped ZnO is thermally unstable. The substitution of Zn 2+ ions with group III ions (B 3+ , Al 3+ , Ga 3+ , and In 3+ ) [8][9][10][11][12][13][14][15][16] generates extra electrons and improves ZnO optical, electrical, thermal, and magnetic properties. Al 3+ has been the most used dopant element due to its small ionic radius and low material cost.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Aluminum Doped Zinc Oxide Nanostructures via Hydrothermal Route

Al-Kahlout

Dahoudi

Grobelsek

et al. 2014

Journal of Materials

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Stable crystalline aluminum doped zinc oxide (AZO) nanopowders were synthesized using hydrothermal treatment processing. Three different aluminum precursors have been used. The Al-precursors were found to affect the morphology of the obtained nanopowders. AZO nanoparticles based on zinc acetate and aluminum nitrate have been prepared with different Al/Zn molar ratios. XRD investigations revealed that all the obtained powders have single phase zincite structure with purity of about 99%. The effect of aluminum doping ratio in AZO nanoparticles (based on Al-nitrate precursor) on structure, phase composition, and particle size has been investigated. The incorporation of Al in ZnO was confirmed by UV-Vis spectroscopy revealing a blue shift due to Burstein-Moss effect.

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Persistent n-type photoconductivity in p-type ZnO

Cited by 113 publications

References 50 publications

UV light-induced changes to the surface conduction in hydrothermal ZnO

UV light-induced changes to the surface conduction in hydrothermal ZnO

Electron and hole traps in N-doped ZnO grown on p-type Si by metalorganic chemical vapor deposition

Synthesis and Characterization of Aluminum Doped Zinc Oxide Nanostructures via Hydrothermal Route

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