Optical properties of undoped and iodine-doped CdTe |
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Authors: | N C Giles Jaesun Lee T H Myers Zhonghai Yu B K Wagner R G Benz C J Summers |
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Affiliation: | (1) Department of Physics, West Virginia University, 26506 Morgantown, WV;(2) EOEML, Quantum Microstructures Laboratory, Georgia Tech Research Institute, 30332 Atlanta, GA |
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Abstract: | A comprehensive study of the properties of undoped and iodine-doped CdTe structures by photoluminescence (PL) and photoreflectance
(PR) is reported. Undoped bulk CdTe and iodine-doped CdTe layers grown by metalorganic molecular beam epitaxy on (lOO)-oriented
CdTe and (211)B-oriented GaAs substrates with electron concentrations ranging from 1014 to mid-1018 cm-3 were included in this study. Lineshape modeling of 80KPL and PR spectra indicated the presence of both free exciton and donor-hole
transitions at the higher doping levels. Strong PL and PR signals were also observed at room temperature. If only a single
transition is considered for the analysis of the 300K spectra, the PL emission peak and the PR transition energy both exhibit
a strong dependence on electron concentration for doped layers. However, lineshape modeling of the room-temperature spectra
indicated the presence of multiple transitions consisting of free exciton and direct band-to-band transitions. The use of
two transitions resulted in a constant value of bandgap over the entire range of conductivities studied. A strong correlation
remained between the broadening of the PR and PL spectra and excess carrier concentration ND-NA. In addition, the E1 transition energy measured by PR was found to vary dramatically with growth conditions. |
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Keywords: | CdTe Metalorganic molecular beam epitaxy (MOMBE) Photoluminescence Photoreflectance |
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