Scattering of charge carriers in transparent and conducting thin oxide films with a non-parabolic conduction band

Pisarkiewicz, T.; Zakrzewska, K.; Leja, E.

doi:10.1016/0040-6090(89)90892-4

Cited by 158 publications

(82 citation statements)

References 11 publications

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“…There is a clear trend for lower mobilities with increasing carrier concentrations that can be attributed to the effect of ionized impurity scattering. [49][50][51] This effect, as well as the influence of grain boundary scattering has been discussed in comprehensive reviews. 30,39,52 As grain boundary scattering plays an important role in films with doping levels in the low 10 20 cm −3 regime we can conclude, that high mobilities can only be reached if the defect density at the grain boundaries can be kept low.…”

Section: Fig 4 ͑Color Online͒ Mobility Determined Hall Measurementsmentioning

confidence: 99%

Improved electrical transport in Al-doped zinc oxide by thermal treatment

Ruske

Roczen

Lee

et al. 2010

Journal of Applied Physics

176

100

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A postdeposition thermal treatment has been applied to sputtered Al-doped zinc oxide films and shown to strongly decrease the resistivity of the films. While high temperature annealing usually leads to deterioration of electrical transport properties, a silicon capping layer successfully prevented the degradation of carrier concentration during the annealing step. The effect of annealing time and temperature has been studied in detail. A mobility increase from values of around 40 cm2/Vs up to 67 cm2/Vs, resulting in a resistivity of 1.4×10−4 Ω cm has been obtained for annealing at temperatures of 650 °C. The high mobility increase is most likely obtained by reduced grain boundary scattering. Changes in carrier concentration in the films caused by the thermal treatment are the result of two competing processes. For short annealing procedures we observed an increase in carrier concentration that we attribute to hydrogen diffusing into the zinc oxide film from a silicon nitride barrier layer between the zinc oxide and the glass substrate and the silicon capping layer on top of the zinc oxide. Both are hydrogen-rich if deposited by plasma-enhanced chemical vapor deposition. For longer annealing times a decrease in carrier concentration can occur if a thin capping layer is used. This can be explained by the deteriorating effect of oxygen during thermal treatments which is well known from annealing of uncapped zinc oxide films. The reduction in carrier concentration can be prevented by the use of capping layers with thicknesses of 40 nm or more.

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Section: Fig 4 ͑Color Online͒ Mobility Determined Hall Measurementsmentioning

confidence: 99%

Improved electrical transport in Al-doped zinc oxide by thermal treatment

Ruske

Roczen

Lee

et al. 2010

Journal of Applied Physics

176

100

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“…According to Pisarkiewicz's model for nonparabolic conduction bands, the Burstein-Moss shift of the bandgap in a heavily doped n-type semiconductor is [22]:…”

Section: Bandgap Shiftmentioning

confidence: 99%

“…Based on Jain's model, in a heavily doped semiconductor, the bandgap renormalization can be described by [14,42] [21,22,37], the relative dielectric constant is 21.9 [43], and the values of Λ and N b are 1 [42]. The three terms in equation (6) represent the exchange energy of the majority carriers, the correlation energy, and the impurity interaction energy, respectively.…”

Section: Bandgap Shiftmentioning

confidence: 99%

“…However, for heavily doped CdO, there has not yet been a systematic report on the dopant-induced bandgap shift which also accounts for the nonparabolicity of the conduction band. All the previous investigations seem to leave out the nonparabolicity or ignore the bandgap renormalization [13,[22][23][24][25][26][27][28]. For a complete understanding of the bandgap shift in doped CdO, an effective theoretical model is needed which considers BGN and a nonparabolic BM shift simultaneously.…”

Section: Introductionmentioning

confidence: 99%

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Structural, optical, and electrical properties of indium-doped cadmium oxide films prepared by pulsed filtered cathodic arc deposition

et al. 2013

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TitleStructural, optical, and electrical properties of indium doped cadmium oxide films prepared by pulsed filtered cathodic arc deposition cm 2 /Vs, and transmittance over 80% (including the glass substrate) from 500-1500 nm. The optical bandgap of the films was found to be in the range of 2.7 to 3.2 eV using both the Tauc relation and the derivative of transmittance. The observed widening of the optical bandgap with increasing carrier concentration can be described well only by considering bandgap renormalization effects along with the Burstein-Moss shift for a nonparabolic conduction band.

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“…Ionized impurity scattering was described by the theory of Brooks 44 and Herring, and Dingle. 45 The analytical expression for the screening function was taken from Pisarkiewicz et al 46 We assumed the films to be uncompensated. Values for the effective mass .…”

Section: B Seed Layer: Temperature Variationmentioning

confidence: 99%

Role of the dopant aluminum for the growth of sputtered ZnO:Al investigated by means of a seed layer concept

Sommer

Stanley

Köhler

et al. 2015

Journal of Applied Physics

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This work elucidates the effect of the dopant aluminum on the growth of magnetron-sputtered aluminum-doped zinc oxide (ZnO:Al) films by means of a seed layer concept. Thin (<100 nm), highly doped seed layers and subsequently grown thick (∼800 nm), lowly doped bulk films were deposited using a ZnO:Al2O3 target with 2 wt. % and 1 wt. % Al2O3, respectively. We investigated the effect of bulk and seed layer deposition temperature as well as seed layer thickness on electrical, optical, and structural properties of ZnO:Al films. A reduction of deposition temperature by 100 °C was achieved without deteriorating conductivity, transparency, and etching morphology which renders these low-temperature films applicable as light-scattering front contact for thin-film silicon solar cells. Lowly doped bulk layers on highly doped seed layers showed smaller grains and lower surface roughness than their counterpart without seed layer. We attributed this observation to the beneficial role of the dopant aluminum that induces an enhanced surface diffusion length via a surfactant effect. The enhanced surface diffusion length promotes 2D-growth of the highly doped seed layer, which is then adopted by the subsequently grown and lowly doped bulk layer. Furthermore, we explained the seed layer induced increase of tensile stress on the basis of the grain boundary relaxation model. The model relates the grain size reduction to the tensile stress increase within the ZnO:Al films. Finally, temperature-dependent conductivity measurements, optical fits, and etching characteristics revealed that seed layers reduced grain boundary scattering. Thus, seed layers induced optimized grain boundary morphology with the result of a higher charge carrier mobility and more suitable etching characteristics. It is particularly compelling that we observed smaller grains to correlate with an enhanced charge carrier mobility. A seed layer thickness of 5 nm was sufficient to induce the beneficial effects.

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Scattering of charge carriers in transparent and conducting thin oxide films with a non-parabolic conduction band

Cited by 158 publications

References 11 publications

Improved electrical transport in Al-doped zinc oxide by thermal treatment

Improved electrical transport in Al-doped zinc oxide by thermal treatment

Structural, optical, and electrical properties of indium-doped cadmium oxide films prepared by pulsed filtered cathodic arc deposition

Role of the dopant aluminum for the growth of sputtered ZnO:Al investigated by means of a seed layer concept

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