Intrinsic and extrinsic doping of ZnO and ZnO alloys

Ellmer, K.; Bikowski, André

doi:10.1088/0022-3727/49/41/413002

Cited by 159 publications

(105 citation statements)

References 299 publications

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“…Mg x Zn 1Àx O is a suitable material for transparent electrode applications for, e.g., thin film solar cells 1,2 due to its large and tunable bandgap, easy n-type dopability, and natural abundance. 3 Recently, new world-record efficiency of 15.5% for pure-sulfide Cu(In,Ga)S 2 thin film solar cell has been reported, where (Mg,Zn)O was used as a buffer layer.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependent self-compensation in Al- and Ga-doped Mg0.05Zn0.95O thin films grown by pulsed laser deposition

Mavlonov

Richter

Wenckstern

et al. 2016

Journal of Applied Physics

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We studied the doping efficiency of Al and Ga dopants in (Mg,Zn)O alloys as a function of the growth temperature and post growth annealing times. High-temperature growth results in the highest structural quality and highest electron mobility; the doping efficiency is limited by the dopant's solubility. It was investigated in detail that a low growth temperature is needed to achieve free carrier densities above the solubility limit of the dopants. Samples grown at temperatures of 300 °C and below have a free carrier density significantly above the solubility limit yielding the minimum resistivity of ρmin=4.8×10−4 Ω cm for Mg0.05Zn0.95O:Al thin films grown on glass at 300 °C. Annealing of these samples reduces the free carrier density and the absorption edge to values similar to those of samples grown at high temperatures. The saturation of the free carrier density and the optical bandgap at their high temperature growth/annealing values is explained by the thermal creation of acceptor-like compensating defects in thermodynamic equilibrium.

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Section: Introductionmentioning

confidence: 99%

Temperature dependent self-compensation in Al- and Ga-doped Mg0.05Zn0.95O thin films grown by pulsed laser deposition

Mavlonov

Richter

Wenckstern

et al. 2016

Journal of Applied Physics

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“…Zinc vacancies introduce states close to the valence band maximum and can take up two electrons [44]. Oxygen interstitials are also considered to be shallow acceptors [55]. Both V Zn and O i have been reported to be the dominant compensating defect in n-type ZnO [44,54].…”

Section: Properties Of Zinc Oxidementioning

confidence: 99%

“…The most common dopants are group III elements, such as B, Al, Ga or In [55]. But also doping with group IV elements, such as Si, Ge, Ti, Zr, Hf, Sn or Pb has been reported [57].…”

Section: Properties Of Zinc Oxidementioning

confidence: 99%

“…For group III elements, the dopant has an additional valence electron as compared to Zn, so it can become easily ionized and introduce an electron into the conduction band of the material. While group IV elements could theoretically supply two electrons in a substitutional site, it Band gap 3.37 eV Figure 2.4: Schematic representation of the energy levels of intrinsic point defects in ZnO [53,55] was found that group IV dopants are present as a trivalent ion and also supply one electron to the conduction band [57]. On the other hand, it is also possible to substitute the oxygen by an group VII element, such as F [58].…”

Section: Properties Of Zinc Oxidementioning

confidence: 99%

“…On the other hand, it is also possible to substitute the oxygen by an group VII element, such as F [58]. Because F has one more valence electron than O, it can also supply an electron to the conduction band [55].…”

Section: Properties Of Zinc Oxidementioning

confidence: 99%

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Deposition of Al-doped ZnO films by high power impulse magnetron sputtering

Mickan¹

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Transparent conducting oxides (TCOs) are an important class of materials with many applications such as low emissivity coatings, or transparent electrodes for photovoltaics and flat panel displays. Among the possible TCO materials, Al-doped ZnO (AZO) is studied due to its relatively low cost and abundance of the raw materials. Thin films of AZO are commonly produced using physical vapour deposition techniques such as magnetron sputtering. However, there is a problem with the homogeneity of the films using reactive direct current magnetron sputtering (DCMS). This homogeneity problem can be related to the bombardment of the growing film with negative oxygen ions, that can cause additional acceptor defects and the formation of insulating secondary phases. In this work AZO films are deposited by high power impulse magnetron sputtering (HiPIMS), a technique in which high instantaneous current densities are achieved by short pulses of low duty cycle.In the first part of this thesis, the possibility to improve the homogeneity of the deposited AZO films by using HiPIMS is demonstrated. This improvement can be related to the high instantaneous sputtering rate during the HiPIMS pulses, so the process can take place in the metal mode. This allows for a lower oxygen ion bombardment of the growing film, which can help to avoid the formation of secondary phases. Another problem of AZO is the stability of the properties in humid environments. To assess this problem, the degradation of the electrical properties after an aging procedure was investigated for films deposited by both DCMS and by HiPIMS. A method was proposed, to restore the properties of the films, using a low temperature annealing under N 2 atmosphere. The improvement of the electrical properties of the films could be related to a diffusion process, where water is diffusing out of the films. Then, the influence of the substrate temperature on the properties of AZO films deposited by HiPIMS was studied. The electrical, optical and structural properties were found to improve with increasing substrate temperature up to 600• C. This improvement can be mostly explained by the increase I in crystalline quality and the annealing of defects. Finally, the deposition of AZO films on flexible PET substrates was investigated. The films are growing as a thick porous layer of preferentially c-axis oriented columns on top of a thin dense seed layer. The evolution of the sheet resistance of the films after bending the films with different radii was studied. There is an increase in the sheet resistance of the films with decreasing bending radius, that is less pronounced for thicker films. II Populärvetenskaplig sammanfattningFör många viktiga tillämpningar i vårt moderna liv, såsom skärmar till mobiltelefoner eller solceller, är det nödvändigt att ha ett transparent material som har en elektrisk ledningsförmåga. Att både vara transparent och vara elektriskt ledande är en ovanlig materialegenskap. Material som är elektriskt ledande, såsom metaller, är vanligtvis inte transp...

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ZnOVaristors: From Grain Boundaries to Power Applications

Greuter

2021

Oxide Electronics

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Intrinsic and extrinsic doping of ZnO and ZnO alloys

Cited by 159 publications

References 299 publications

Temperature dependent self-compensation in Al- and Ga-doped Mg0.05Zn0.95O thin films grown by pulsed laser deposition

Temperature dependent self-compensation in Al- and Ga-doped Mg0.05Zn0.95O thin films grown by pulsed laser deposition

Deposition of Al-doped ZnO films by high power impulse magnetron sputtering

ZnOVaristors: From Grain Boundaries to Power Applications

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