Optical and electrical characterization of cadmium selenide doped with cobalt |
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Authors: | Ming Luo Chunchuan Xu A Burger |
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Institution: | a Physics Department, West Virginia University, Morgantown, WV 26506-6315, USA b Physics Department, Fisk University, Nashville, TN 37208-3051, USA |
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Abstract: | The optical and electrical properties of Co2+ ions in CdSe have been investigated. Absorption, photoluminescence, electron paramagnetic resonance, and Hall measurements were used to characterize a cobalt-doped (1×1019 cm−3) single crystal. Infrared absorption and emission spectra associated with transitions between the 4A2(F) ground state and the 4T1(F) and 4T2(F) excited states are described. At 10 K, spin-orbit splittings result in three structured absorption bands associated with the 4A2(F) to 4T1(F) transition having zero-phonon lines at 4926, 5101, and 5724 cm−1. The 4A2(F) to 4T2(F) transition shows two zero-phonon lines at 2874 and 3286 cm−1, also accompanied by vibronic structure. Intrinsic lattice modes explain most of the sharp-line structure observed at low temperature, except for a subset of peaks where local modes (25-30 cm−1) are invoked. Using below-band-gap light, selective excitation allows detection of the 4T1(F) to 4A2(F) recombination at liquid-helium temperatures. The activation of free carriers in our n-type material containing shallow donors is affected by the presence of cobalt, and we find the Co+/++ level to be about 34 meV below the conduction band of CdSe. |
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Keywords: | A Semiconductors C Infrared spectroscopy D Luminescence D Electrical properties D Electron paramagnetic resonance (EPR) |
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