Differences in n-type doping efficiency between Al- and Ga-ZnO films

Gabás, M.; Landa-Cánovas, A.R.; Costa‐Krämer, J. L.; Agulló-Rueda, F.; González‐Elipe, Agustín R.; Díaz-Carrasco, Pilar; Hernández-Moro, J.; Lorite, I.; Herrero, Pilar; Castillero, Pedro; Barranco, Ángel; Ramos-Barrado, J.R.

doi:10.1063/1.4803063

Cited by 71 publications

(38 citation statements)

References 35 publications

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“…Due to its size, Al can also be incorporated interstitially in the octahedral void in ZnO, where it does not act as donor [36]. Ga, on the other hand, is more prone to substitutional incorporation and thus introduces more efficiently charge carriers [37]. The carrier density of the IZO films is only slightly higher than for ZnO.…”

Section: Optical and Electrical Propertiesmentioning

confidence: 85%

Comparison of chemical bath-deposited ZnO films doped with Al, Ga and In

et al. 2017

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A comparative study is presented on chemical bath-deposited ZnO films, doped with the group-13 metals Al, Ga and In. The study reveals marked differences in dopant incorporation in the films, which increases in the order: In, Al and Ga. The presence of dopant in the solution induces significant modifications in the deposition rate, which varies between 110 and 40 nm min -1 . All films are (002)-textured, whereas the lattice stress evolution with the dopant type and concentration suggests that Ga has the highest degree of substitutional incorporation in Zn sites. The average visible transmittance is higher than 80%, while the infrared reflectivity depends on the free carrier density in the films, which is the lowest for undoped ZnO and increases in the order: In-, Al-and Ga-doped ZnO. Optical measurements also yield an inverse correlation between carrier density and mobility. Doping enlarges the bandgap, as well as the Urbach energy that is related to the films' disorder. The lowest electrical resistivity, measured by fourpoint probe, is 1.7 9 10 -2 X cm and is obtained for In-doped films after being exposed to ultraviolet light. Ga-doped films are found to exhibit the highest stability of the conductivity upon ultraviolet exposure.

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Section: Optical and Electrical Propertiesmentioning

confidence: 85%

Comparison of chemical bath-deposited ZnO films doped with Al, Ga and In

et al. 2017

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“…If each impurity donated one electron to the CB, the optical gap variation would be 0.93 and 0.89 eV for Al-and GaeZnO, respectively. However, it is found experimentally that GaeZnO increases its gap by only 0.42 eV, while for AleZnO the increment is 0.04 eV [11]. Therefore, the dopant cations have to be partially compensated by acceptor defects that would reduce the carrier density at the CB.…”

Section: Resultsmentioning

confidence: 94%

“…The GaeZnO film carrier density deduced from Hall effect measurements [11] is one order of magnitude larger than for AleZnO (5 Â 10 20 vs 3 Â 10 19 cm À3 ). From these carrier concentrations, a conduction band (CB) population of 0.7 and 0.04 electrons per dopant atom can be inferred in GaeZnO and AleZnO, respectively.…”

Section: Introductionmentioning

confidence: 98%

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Electronic and atomic structure of complex defects in Al- and Ga-highly doped ZnO films

Menéndez-Proupín

Palacios

Wahnón

2015

Materials Chemistry and Physics

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Artículo de publicación ISIPoint defects in Ga- and Al-doped ZnO thin films are studied by means of first principles electronic structure calculations. Candidate defects are identified to explain recently observed differences in electrical and spectroscopic behavior of both systems. Substitutional doping in Ga-ZnO explain the metallic behavior of the electrical properties. Complexes of interstitial oxygen with substitutional Ga can behave as acceptor and cause partial compensation, as well as gap states below the conduction band minimum as observed in photoemission experiments. Zn vacancies can also act as compensating acceptors. On the other hand, the semiconducting behavior of Al-ZnO and the small variation in the optical gap compared with pure ZnO, can be explained by almost complete compensation between acceptor Zn vacancies and substitutional Al donors. Interstitial Al can also be donor levels and can be the origin of the small band observed in photoemission experiments below the Fermi level. Combinations of substitutional Al with interstitial oxygen can act simultaneously as compensating acceptor and generator of the mentioned photoemission band. The theoretical calculations have been done using density functional theory (DFT) within the generalized gradient approximation with on-site Coulomb interaction. In selected cases, DFT calculations with semilocal-exact exchange hybrid functionals have been performed. Results explain photoelectron spectra of Ga-ZnO and Al-ZnO at the corresponding doping levels

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“…ions and thus add free electrons [18][19][20]. In particular, according to previous reports, In-or Ga-doped ZnO thin films exhibited resistivities as low as *10 -3 X cm, while Al doping lowered the resistivity to the order of 10 -2 X cm [21,22]. However, doping of In in ZnO thin films reveals various issues such as degradation of ZnO crystallinity [23][24][25], deterioration of electrical resistivity with the increase in doping level [24,26,27], decrease in carrier concentration or mobility [28][29][30], and an increase in surface roughness [31].…”

mentioning

confidence: 81%

Improvement in electrical properties of sol–gel-derived In-doped ZnO thin film by electron beam treatment

Kim

et al. 2015

J Sol-Gel Sci Technol

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In-doped ZnO thin films were prepared by a sol-gel spin coating method. Since several issues with In doping have been reported, such as degradation of crystallinity and deterioration of electrical resistivity at high Indoping levels, co-doping with Ga and electron beam treatment was demonstrated in this study. When In dopant was added to the ZnO thin film at 0.5 mol%, it increased the carrier concentration, thereby reducing the resistivity of the film. In contrast, further doping by Ga in the presence of In did not significantly change the electrical properties. When electron beam treatment was conducted on ZnO films, the optical band gap was increased and the carrier concentration and mobility were increased. In particular, a 0.5 mol% Indoped ZnO that received electron beam treatment at 2 keV exhibited an electrical resistivity as low as 4.8 9 10 -2 X cm, while 57.1 X cm was obtained from the pristine ZnO thin film. When the ZnO films were applied to crystalline Si solar cells, conversion efficiency significantly increased from 10.37 % for the cell with pristine ZnO thin film to 11.45 % with the In-doped and electron beamtreated ZnO thin film. Graphical Abstract 10

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Differences in n-type doping efficiency between Al- and Ga-ZnO films

Cited by 71 publications

References 35 publications

Comparison of chemical bath-deposited ZnO films doped with Al, Ga and In

Comparison of chemical bath-deposited ZnO films doped with Al, Ga and In

Electronic and atomic structure of complex defects in Al- and Ga-highly doped ZnO films

Improvement in electrical properties of sol–gel-derived In-doped ZnO thin film by electron beam treatment

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