Self-compensation in semiconductors: The Zn vacancy in Ga-doped ZnO

Look, David C.; Leedy, Kevin D.; Vines, Lasse; Svensson, B. G.; Zubiaga, A.; Tuomisto, Filip; Doutt, Daniel R.; Brillson, L. J.

doi:10.1103/physrevb.84.115202

Cited by 185 publications

(201 citation statements)

References 26 publications

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“…Earlier studies on ZnO show that defects related to single Zn vacancies are the main defects observed with positron annihilation spectroscopy. This is seen in both undoped and Al/Ga-doped thin films 21,[26][27][28] as well as in studies in bulk crystals. [10][11][12]22,25 Clusters of vacancies in ZnO have been observed mainly in implantation studies 4,23,[29][30][31][32][33][34][35][36][37][38] and also after heavy irradiation.…”

Section: Discussionmentioning

confidence: 99%

Nitrogen and vacancy clusters in ZnO

et al. 2013

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Section: Discussionmentioning

confidence: 99%

Nitrogen and vacancy clusters in ZnO

et al. 2013

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“…The difference in the annealing behavior is tentatively attributed to the lower concentration of compensating defects in GZO grown under metal-rich conditions. 12 For highly conductive GZO with electrical properties comparable to our best GZO grown under metal-rich conditions, Look et al 30 reported the existence of Zn-vacancy-related acceptors causing selfcompensation based on positron annihilation measurements and secondary-ion mass spectroscopy (SIMS). This seems consistent with our observation of slight increase in both the electron concentration and mobility upon annealing for one GZO layer grown under metal-rich conditions (n ¼ 8.33 Â 10 20 cm À3 and l ¼ 36.7 cm 2 =VÁs in the as-grown sample vs. n ¼ 9.23 Â 10 20 cm À3 , l ¼ 42.4 cm 2 =VÁs in the annealed one).…”

Section: Resultsmentioning

confidence: 99%

Electron scattering mechanisms in GZO films grown on a-sapphire substrates by plasma-enhanced molecular beam epitaxy

Liu¹,

Avrutin²,

Izyumskaya³

et al. 2012

Journal of Applied Physics

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We report on the mechanisms governing electron transport using a comprehensive set of ZnO layers heavily doped with Ga (GZO) grown by plasma-enhanced molecular-beam epitaxy on a-plane sapphire substrates with varying oxygen-to-metal ratios and Ga fluxes. The analyses were conducted by temperature dependent Hall measurements which were supported by microstructural investigations as well. Highly degenerate GZO layers with n > 5 Â 10 20 cm À3 grown under metalrich conditions (reactive oxygen-to-metal ratio <1) show relatively larger grains ($20-25 nm by x-ray diffraction) with low-angle boundaries parallel to the polar c-direction. For highly conductive GZO layers, ionized-impurity scattering with almost no compensation is the dominant mechanism limiting the mobility in the temperature range from 15 to 330 K and the grain-boundary scattering governed by quantum-mechanical tunnelling is negligible. However, due to the polar nature of ZnO having high crystalline quality, polar optical phonon scattering cannot be neglected for temperatures above 150 K, because it further reduces mobility although its effect is still substantially weaker than the ionized impurity scattering even at room temperature (RT). Analysis of transport measurements and sample microstructures by x-ray diffraction and transmission electron microscopy led to a correlation between the grain sizes in these layers and mobility even for samples with a carrier concentration in the upper 10 20 cm À3 range. In contrast, electron transport in GZO layers grown under oxygen-rich conditions (reactive oxygen-to-metal ratio >1), which have inclined grain boundaries and relatively smaller grain sizes of 10-20 nm by x-ray diffraction, is mainly limited by compensation caused by acceptor-type point-defect complexes, presumably (Ga Zn -V Zn ), and scattering on grain boundaries. The GZO layers with n <10 20 cm À3 grown under metal-rich conditions with reduced Ga fluxes show a clear signature of grain-boundary scattering governed by the thermionic effect in the temperature-dependent mobility but with much higher RT mobility values compared to the samples grown under oxygen-rich conditions [34 vs. 7.5 cm 2 =VÁs]. Properties of GZO layers grown under different conditions clearly indicate that to achieve highly conductive GZO, metal-rich conditions instead of oxygen-rich conditions have to be used. V C 2012 American Institute of Physics. [http://dx

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“…Thus, the photo-degraded and proton irradiated perovskite should be considered as a partially compensated semiconductor. [15,[39][40][41] Moreover, the proton induced point defects and fragments of CH3NH3 may also form defect related complexes. [42,43] It is possible that these complex defects do not participate in recombination processes.…”

Section: Discussionmentioning

confidence: 99%