Electronic properties of defects in pulsed-laser deposition grown ZnO with levels at 300 and 370meV below the conduction band

Auret, F.D.; Meyer, W.E.; Rensburg, P.J. Janse van; Hayes, M.; Nel, Jackie M.; Wenckstern, Holger von; Schmidt, Heidemarie; Biehne, G.; Hochmuth, H.; Lorenz, Michael; Grundmann, Marius

doi:10.1016/j.physb.2007.08.192

Cited by 32 publications

(36 citation statements)

References 11 publications

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“…26 In addition to the commonly observed trap E 3 ͑0.3 eV͒, another close lying peak E 3 Ј ͑0.37 eV͒ was observed by using high resolution Laplace-transform DLTS in ZnO grown by pulsed-laser deposition. 27 An increase in the concentration of E 3 Ј after annealing in oxygen suggested that the trap could be associated with O. In that study, however, E 3 Ј was not found in a bulk ZnO grown by the vaporphase technique ͑serving as a reference͒.…”

Section: Resultsmentioning

confidence: 72%

Surface traps in vapor-phase-grown bulk ZnO studied by deep level transient spectroscopy

Fang

Claflin

Dong

et al. 2008

Journal of Applied Physics

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Deep level transient spectroscopy, current-voltage, and capacitance-voltage measurements are used to study interface traps in metal-on-bulk-ZnO Schottky barrier diodes ͑SBDs͒. c-axis-oriented ZnO samples were cut from two different vapor-phase-grown crystals, and Au-and Pd-SBDs were formed on their ͑0001͒ surfaces after remote oxygen-plasma treatment. As compared to Au-SBDs, the Pd-SBDs demonstrated higher reverse-bias leakage current and forward-bias current evidently due to higher carrier concentrations, which might have been caused by hydrogen in-diffusion through the thin Pd metal. The dominant traps included the well-known bulk traps E 3 ͑0.27 eV͒ and E 4 ͑0.49 eV͒. In addition, a surface-related trap, E s ͑0.49 eV͒, is observed but only in the Pd-SBDs, not in the Au-SBDs. Trap E s is located at depths less than about 95 nm and shows an electron capture behavior indicative of extended defects. A possible correspondence between trap E s and the well-known 2.45 eV green band is suggested by depth-resolved cathodoluminescence spectroscopy on the same samples, which reveals an increase in the intensity of this band within ϳ100 nm of the Pd/ZnO interface.

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Section: Resultsmentioning

confidence: 72%

Surface traps in vapor-phase-grown bulk ZnO studied by deep level transient spectroscopy

Fang

Claflin

Dong

et al. 2008

Journal of Applied Physics

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“…However, in addition to the commonly observed trap E3 ͑0.3 eV͒, another close lying peak E3Ј ͑0.37 eV͒ was reported by using high resolution Laplace-transform DLTS in ZnO grown by pulsed-laser deposition. 11 An increase in the concentration of E3Ј after annealing in oxygen suggested that this new trap could be associated with oxygen incorporation. In that study, however, E3Ј was not found in any bulk-grown ZnO ͑serving as a reference͒.…”

Section: Observation Of Surface Traps On Zn Facementioning

confidence: 99%

Metal contacts on bulk ZnO crystal treated with remote oxygen plasma

Fang

Claflin

Dong

et al. 2009

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

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To study the quality of thin metal/ZnO Schottky contacts ͑SCs͒, temperature-dependent current-voltage ͑I-V͒, capacitance-voltage, deep level transient spectroscopy, and photoluminescence measurements were performed using bulk, vapor-phase ZnO, treated by remote oxygen plasma ͑ROP͒. Au/ ZnO and Pd/ ZnO contacts on both O and Zn faces are compared as a function of the ROP processing sequence and duration. We find that ͑i͒ as the duration of ROP treatment increases from 2 to 4 h, Au/ ZnO contacts on the Zn face, deposited before ROP treatment, become rectifying, while those on the O face remain Ohmic; ͑ii͒ with long-term ROP treatments prior to metallization, both Au/ ZnO and Pd/ ZnO show high-quality SCs; however, their I-V characteristics can be significantly degraded by electric field and high temperatures; ͑iii͒ ROP treatment can cause more H removal on the Zn face than on the O face, resulting in a decrease in the near-surface carrier concentration for the Zn face only; ͑iv͒ in addition to the dominant bulk-trap E3, surface traps, E6/E7 and E8, and Es, can be observed in Au/ ZnO and Pd/ ZnO SCs, respectively, on the Zn face, with shorter ROP treatment; and ͑v͒ with long-term ROP treatment, E3 ͑or L2͒ significantly increases and shifts in Au/ ZnO SCs on the Zn face.

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“…In the literature, defects in ZnO (single crystal or sputtered lm) with similar energy values have been observed in DLTS and impedance spectroscopy. [52][53][54][55][56] Ref. 53 suggests that these defects might relate to the incorporation of oxygen in the crystal lattice.…”

Section: 49mentioning

confidence: 99%

“…[52][53][54][55][56] Ref. 53 suggests that these defects might relate to the incorporation of oxygen in the crystal lattice. We emphasize that the origin of defects in ZnO is generally under debate in the literature [52][53][54][55][56][57][58] and that a direct comparison with the literature needs to be done with caution, as the defect density is sensitively affected by the growth method and annealing conditions.…”

Section: 49mentioning

confidence: 99%

Charge transport in nanoparticular thin films of zinc oxide and aluminum-doped zinc oxide

et al. 2015

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In this work, we report on the electrical characterization of nanoparticular thin films of zinc oxide (ZnO) and aluminum-doped ZnO (AZO). Temperature-dependent current-voltage measurements revealed that charge transport for both, ZnO and AZO, is well described by the Poole-Frenkel model and excellent agreement between the experimental data and the theoretical predictions is demonstrated. For the first time it is shown that the nature of the charge-transport is not affected by the doping of the nanoparticles and it is proposed that the Poole-Frenkel effect is an intrinsic and universally limiting mechanism for the charge transport in nanoparticular thin films with defect states within the bandgap. and also thin-lm solar cells, where it can serve as an active 10,11 or interfacial 12,13 or electrode material.14 Moreover, ZnO is a promising material in the eld of transparent 3,4,15 and exible electronics, 15,16 because large-area solution processing on exible substrates using techniques like inkjet printing appears feasible.17,18 The solutions for lm deposition are either based on the sol-gel route or on nanoparticle synthesis. The latter has the advantage that the synthesis and the lm deposition can be separated from each other. As pointed out previously, 19,20 this allows cheap and highthroughput synthesis at elevated temperatures, while the lm deposition is achieved at lower temperatures, which is a prerequisite for the use of exible (oen polymer-based) substrates.The problem of nanoparticulate ZnO thin lms deposited at low temperatures is that they hardly reach the electric performance of zinc oxide lms based on sputtering 21 or spray pyrolysis.22 Therefore, a better understanding of the electric conduction in these lms is desired.So far, most of the charge transport studies on ZnO nanoparticle lms used the transistor device structure: Meulenkamp 23 and Roest et al. 24,25 studied ZnO nanoparticles with small sizes (z5 nm) permeated in electrolyte solutions and it was demonstrated that transport occurs via tunnelling between discrete electronic states with or without additional thermal activation depending on the characteristics of the electrolyte. 25Besides, space-charge limited conduction (SCLC) was shown for ZnO by Bubel et al. 19 and by Caglar et al. 26 (sandwich device geometry). In these two cases, 19,26 the sizes of the nanostructures were larger (above 25 nm) compared to the abovementioned reports. This might partially explain the different ndings.Discrepancies between various transport investigations were also revealed for other nanoparticular materials, e.g. for nanostructured lms of silicon. Besides hopping, 27,28 SCLC, 29 the Poole-Frenkel effect, 30,31 and tunnelling 32,33 were reported for nano-Si (porous silicon or nanoparticles). These inconsistent results further emphasize the need for a detailed description of charge transport in nanoparticular lms.In this work, the charge transport of nanoparticulate ZnO and AZO thin lms was investigated. A dispersion of ligandstabilized ZnO or...

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Electronic properties of defects in pulsed-laser deposition grown ZnO with levels at 300 and 370meV below the conduction band

Cited by 32 publications

References 11 publications

Surface traps in vapor-phase-grown bulk ZnO studied by deep level transient spectroscopy

Surface traps in vapor-phase-grown bulk ZnO studied by deep level transient spectroscopy

Metal contacts on bulk ZnO crystal treated with remote oxygen plasma

Charge transport in nanoparticular thin films of zinc oxide and aluminum-doped zinc oxide

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