8 February 2007 Optical properties of n- and p-type ZnO thin films: two different approaches to the impurity distribution inhomogeneity
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We investigated the optical properties of epitaxial n- and p-type ZnO films grown on lattice-matched ScAlMgO4 substrates. Chemical doping yielded a severe inhomogeneity in a statistical distribution of involved charged impurities. Two approaches are adopted to treat the inhomogeneity effects; Monte Carlo simulation technique for the n-doped films, and the fluctuation theory for the p-ZnO. The broadening of PL band of n-ZnO was significantly larger than predicted by theoretical results in which the linewidths of each individual emissions have been determined mainly from the concentration fluctuation of donor-type dopants by the simulation. Moreover, the rather asymmetrical line shape was observed. To explain these features, a vibronic model was developed accounting for contributions from a series of phonon replicas. In case of p-type ZnO:N, analysis of excitation-intensity dependence of the peak shift of donor-acceptor luminescence with a fluctuation model has also proven the importance of the inhomogeneity effect of charged impurity distribution, as in the case of ZnO:Ga. We extracted the inhomogeneity in the sample and acceptor activation energy prepared under the various growth conditions. It is shown that the theoretical results are in good agreement with the experimental 5-K time-resolved luminescence for the systems in a fluctuation field. Finally, localized-state distributions have been studied in N-doped ZnO thin films by means of transient photocurrent measurement.
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Takayuki Makino, Takayuki Makino, } "Optical properties of n- and p-type ZnO thin films: two different approaches to the impurity distribution inhomogeneity", Proc. SPIE 6471, Ultrafast Phenomena in Semiconductors and Nanostructure Materials XI and Semiconductor Photodetectors IV, 64710K (8 February 2007); doi: 10.1117/12.697515; https://doi.org/10.1117/12.697515

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