Barrier-controlled carrier transport in microcrystalline semiconducting materials: Description within a unified model

Weis, T.; Lipperheide, R.; Wille, U.; Brehme, S.

doi:10.1063/1.1488246

Cited by 93 publications

(60 citation statements)

References 23 publications

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“…Recently, Lipperheide and Wille [26][27][28] worked out a theory for the combined ballistic and diffusive transport across grain barriers, which was applied to the carrier transport in polycrystalline silicon films [29,30]. However, their numerical approach yields only a marginal improvement compared to the analytical model of Seto.…”

Section: Ionized Impurity Scatteringmentioning

confidence: 99%

Carrier transport in polycrystalline transparent conductive oxides: A comparative study of zinc oxide and indium oxide

Ellmer

Mientus²

2008

Thin Solid Films

330

191

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Highly-doped indium-tin oxide films exhibit resistivities ρ as low as 1. . Thus the grain barrier trap densities of ZnO and ITO are significantly different, which seems to be connected with the defect chemistry of the two oxides and especially with the piezoelectricity of zinc oxide.Keywords Transparent conductive oxides, carrier transport, degenerate semiconductors, grain barriers, electron mobility 2 Therefore, in the present study the carrier transport processes in ITO and ZnO are compared in order to get a deeper understanding of the differences between these TCO materials. For this purpose conductivity and Hall mobility measurements on ZnO:Al and ITO films were undertaken for films deposited on amorphous as well as single crystalline substrates (sapphire) in order to determine the dominant scattering processes (ionized impurities, grain barriers, crystallographic defects). Our own data are compared with literature data reported for ZnO and ITO to show the general trends. Theoretical and semiempirical models are used to fit the experimental data and to derive characteristic material parameters for these three oxides. Introduction Theoretical modelsThe theoretical models on ionized impurity scattering were already reviewed in 2001 by one of the authors when estimating the mobility limit of highly-doped zinc oxide [3]. In the following a short summary is given to lay the basis for the further discussion.Ionized impurity scattering. This scattering process is caused by ionized dopant atoms and dominates for carrier concentrations above about 10 19 cm -3. An analytical expression for the mobility µ ii of degenerately doped semiconductors, taking into account the non-parabolicity of the conduction band, was given by Zawadzki [7] and refined by Pisarkiewicz et al. [6]:where the screening functionwith the parameter ξ np =1-m 0 */m*, which describes the non-parabolicity of the conduction band (m*, m 0 * -effective masses in the conduction band and at the conduction band edge, 4 respectively). The prefactor in equ. (1) The fit parameters µ max , µ min and µ min -µ 1 describe the lattice mobility at low carrier concentrations, the mobility limited by ionized impurity scattering and the clustering mobility, discussed above (see Table 2). . The ZnO mobility values were fitted using the empirical formula (3) and the fit parameters are summarized in Table 2 together with the corresponding values for silicon. In the transition region from lattice to ionized scattering for 5 . 10 16 < N < 5 . 10 18 cm -3 a large scattering of the experimental ZnO data can be observed. Therefore, the data have been fitted in analogy to the silicon data, which exhibit a much higher accuracy [14].However, the exact transition does not influence the conclusions much since we are interested predominantly in ionized impurity scattering in the region N > 10 19 cm -3 .5 Neutral impurity scattering. Neutral shallow-impurity scattering is often discussed in papers about transport in TCO films at room temperature [17,18]. The mobility due to ...

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Section: Ionized Impurity Scatteringmentioning

confidence: 99%

Carrier transport in polycrystalline transparent conductive oxides: A comparative study of zinc oxide and indium oxide

Ellmer

Mientus²

2008

Thin Solid Films

330

191

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“…One is naturally drawn to models for electrical transport that are based on the effective-mass theory, which would seem to apply at least within a crystallite. Indeed this approach has been applied recently to Hall mobility measurements in n-type microcrystalline silicon [8]. It is thus a bit of a shock to discover that the multiple-trapping model taken from amorphous semiconductors is a better description of microcrystalline silicon than is an effective-mass based approach -but this is the implication of our measurements.…”

Section: Introductionmentioning

confidence: 38%

“…One approach to analyzing mobilities in polycrystalline materials is to invoke the effective masses that would obtain for electrons and holes in the single crystal, and assume that the grain boundaries act as scatterers or barriers and as the locus for traps for the carriers [8]. It is instructive to use this approach crudely to calculate an "effective-mass carrier mobility" for holes Table I.…”

Section: Meaning Of Multiple Trapping In Microcrystalline Siliconmentioning

confidence: 99%

Hole Drift-Mobility Measurements and Multiple-Trapping in Microcrystalline Silicon

2004

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We present photocarrier time-of-flight measurements of the hole drift-mobility in microcrystalline silicon samples with a high crystalline volume fraction; typical roomtemperature values are about 1 cm 2 /Vs. Temperature-dependent measurements are consistent with the model of multiple-trapping in an exponential bandtail. While this model has often been applied to amorphous silicon, its success for predominantly crystalline samples is unexpected. The valence bandtail width is 31 meV, which is about 10-20 meV smaller than values reported for a-Si:H, and presumably reflects the greater order in the microcrystalline material. The hole band-mobility is about 1 cm 2

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“…The enhanced ethanol gas sensing performance of the Cr2O3 nanoparticle-decorated ZnS nanorod sensor can be explained by modulation of the conduction channel width [50] and the potential barrier height at the ZnS-Cr2O3 interface [27,28]. (Cr2O3) is not available at present, a large portion of the total volume of each Cr2O3 nanoparticle might be depleted of carriers in air.…”

Section: Gas-sensing Mechanismmentioning

confidence: 99%

Prominent ethanol sensing with Cr2O3 nanoparticle-decorated ZnS nanorods sensors

Sun

Kheel

et al. 2016

Journal of the Korean Physical Society

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ZnS nanorods and Cr2O3 nanoparticle-decorated ZnS nanorods were synthesized using facile hydrothermal techniques and their ethanol sensing properties were examined. Xray diffraction and scanning electron microscopy revealed the good crystallinity and size uniformity of the ZnS nanorods. The Cr2O3 nanoparticle-decorated ZnS nanorod sensor showed stronger response to ethanol than the pristine ZnS nanorod sensor. The responses of the pristine and decorated nanorod sensors to 200 ppm of ethanol at 300°C were 2.9 and 13.8, respectively. Furthermore, under these conditions, the decorated nanorod sensor showed longer response time (23 s) and shorter recovery time (20 s) than those of the pristine one (19 and 35 s, respectively). Consequently, the total sensing time of the decorated nanorod sensor (42 s) was shorter than that of the pristine one (55 s). The decorated nanorod sensor showed excellent selectivity to ethanol over other volatile organic compound gases including acetone, methanol, benzene, toluene, whereas the pristine one failed to show selectivity to ethanol over acetone. The improved sensing performance of the decorated nanorod sensor is attributed to the modulation of the conduction channel width and the potential barrier height at the ZnS-Cr2O3 interface 1 accompanying the adsorption and desorption of ethanol gas as well as the greater surface-to-volume ratio of the decorated nanorods than the pristine one due to the existence of the ZnS-Cr2O3 interface.PACS number: 81.07. 81.05.Ea, 81.15.Gh,

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Barrier-controlled carrier transport in microcrystalline semiconducting materials: Description within a unified model

Cited by 93 publications

References 23 publications

Carrier transport in polycrystalline transparent conductive oxides: A comparative study of zinc oxide and indium oxide

Carrier transport in polycrystalline transparent conductive oxides: A comparative study of zinc oxide and indium oxide

Hole Drift-Mobility Measurements and Multiple-Trapping in Microcrystalline Silicon

Prominent ethanol sensing with Cr2O3 nanoparticle-decorated ZnS nanorods sensors

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