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Title: Iodine Doping of CdTe and CdMgTe for Photovoltaic Applications

Abstract

Here, iodine-doped CdTe and Cd 1-xMg xTe layers were grown by molecular beam epitaxy. Secondary ion mass spectrometry characterization was used to measure dopant concentration, while Hall measurement was used for determining carrier concentration. Photoluminescence intensity and time-resolved photoluminescence techniques were used for optical characterization. Maximum n-type carrier concentrations of 7.4 x 10 18 cm -3 for CdTe and 3 x 10 17 cm -3 for Cd 0.65Mg 0.35Te were achieved. Studies suggest that electrically active doping with iodine is limited with dopant concentration much above these values. Dopant activation of about 80% was observed in most of the CdTe samples. The estimated activation energy is about 6 meV for CdTe and the value for Cd 0.65Mg 0.35Te is about 58 meV. Iodine-doped samples exhibit long lifetimes with no evidence of photoluminescence degradation with doping as high as 2 x 10 18 cm -3, while indium shows substantial non-radiative recombination at carrier concentrations above 5 x 10 16 cm -3. Iodine was shown to be thermally stable in CdTe at temperatures up to 600 °C. Results suggest iodine may be a preferred n-type dopant compared to indium in achieving heavily doped n-type CdTe.

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [2];  [3];  [2];  [1]
  1. Texas State Univ., San Marcos, TX (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  3. EAG Laboratories, Sunnyvale, CA (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1374126
Report Number(s):
NREL/JA-5K00-68892
Journal ID: ISSN 0361-5235
Grant/Contract Number:
AC36-08GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Electronic Materials
Additional Journal Information:
Journal Volume: 46; Journal Issue: 9; Journal ID: ISSN 0361-5235
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CdTe; Cd1-xMgxTe; doping; iodine; MBE; solar cell

Citation Formats

Ogedengbe, O. S., Swartz, C. H., Jayathilaka, P. A. R. D., Petersen, J. E., Sohal, S., LeBlanc, E. G., Edirisooriya, M., Zaunbrecher, K. N., Wang, A., Barnes, T. M., and Myers, T. H.. Iodine Doping of CdTe and CdMgTe for Photovoltaic Applications. United States: N. p., 2017. Web. doi:10.1007/s11664-017-5588-4.
Ogedengbe, O. S., Swartz, C. H., Jayathilaka, P. A. R. D., Petersen, J. E., Sohal, S., LeBlanc, E. G., Edirisooriya, M., Zaunbrecher, K. N., Wang, A., Barnes, T. M., & Myers, T. H.. Iodine Doping of CdTe and CdMgTe for Photovoltaic Applications. United States. doi:10.1007/s11664-017-5588-4.
Ogedengbe, O. S., Swartz, C. H., Jayathilaka, P. A. R. D., Petersen, J. E., Sohal, S., LeBlanc, E. G., Edirisooriya, M., Zaunbrecher, K. N., Wang, A., Barnes, T. M., and Myers, T. H.. Tue . "Iodine Doping of CdTe and CdMgTe for Photovoltaic Applications". United States. doi:10.1007/s11664-017-5588-4.
@article{osti_1374126,
title = {Iodine Doping of CdTe and CdMgTe for Photovoltaic Applications},
author = {Ogedengbe, O. S. and Swartz, C. H. and Jayathilaka, P. A. R. D. and Petersen, J. E. and Sohal, S. and LeBlanc, E. G. and Edirisooriya, M. and Zaunbrecher, K. N. and Wang, A. and Barnes, T. M. and Myers, T. H.},
abstractNote = {Here, iodine-doped CdTe and Cd1-xMgxTe layers were grown by molecular beam epitaxy. Secondary ion mass spectrometry characterization was used to measure dopant concentration, while Hall measurement was used for determining carrier concentration. Photoluminescence intensity and time-resolved photoluminescence techniques were used for optical characterization. Maximum n-type carrier concentrations of 7.4 x 1018 cm-3 for CdTe and 3 x 1017 cm-3 for Cd0.65Mg0.35Te were achieved. Studies suggest that electrically active doping with iodine is limited with dopant concentration much above these values. Dopant activation of about 80% was observed in most of the CdTe samples. The estimated activation energy is about 6 meV for CdTe and the value for Cd0.65Mg0.35Te is about 58 meV. Iodine-doped samples exhibit long lifetimes with no evidence of photoluminescence degradation with doping as high as 2 x 1018 cm-3, while indium shows substantial non-radiative recombination at carrier concentrations above 5 x 1016 cm-3. Iodine was shown to be thermally stable in CdTe at temperatures up to 600 °C. Results suggest iodine may be a preferred n-type dopant compared to indium in achieving heavily doped n-type CdTe.},
doi = {10.1007/s11664-017-5588-4},
journal = {Journal of Electronic Materials},
number = 9,
volume = 46,
place = {United States},
year = {Tue Jun 06 00:00:00 EDT 2017},
month = {Tue Jun 06 00:00:00 EDT 2017}
}

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  • Individual quantum dots are produced by selective interdiffusion between the barriers and the quantum well layer in a CdTe/CdMgTe heterostructure. The heterostructure, with a SiO{sub 2} mask preliminarily deposited onto the surface, was subjected to short-term annealing for 1 min at the temperature 410 deg. C. The mask contained open apertures with diameter up to 140 nm. The annealing induces diffusion of Mg atoms into the depth of the quantum well. Diffusion is substantially enhanced under the mask. The induced lateral potential, with minimums in the regions of apertures of the mask, stimulates efficient localization of charge carriers that formmore » quasi-zero-dimensional excitons. The study of radiative recombination suggests complete spatial confinement of the excitons. The confinement manifests itself in the observation of a substantially narrowed line of excitonic transitions, as well as in the observation of biexcitons and excited states at high levels of photoexcitation. The characteristic energies of interlevel splitting and the biexciton binding energy show that charge carriers are under the condition of weak confinement in the quantum dots.« less
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  • CdTe/MnTe/CdMgTe quantum-well structures with one or two monolayers of MnTe inserted at CdTe/CdMgTe interfaces were fabricated. The spectra of the excitonic luminescence from CdTe quantum wells and their variation with temperature indicate that introduction of ultrathin MnTe layers improves the interface quality. The effect of a magnetic field in the Faraday configuration on the spectral position of the exciton-emission peaks indicates that frustration of magnetic moments in one-monolayer MnTe insertions is weaker than in two-monolayer insertions. The effect of a magnetic field on the exciton localization can be explained in terms of the exciton wave-function shrinkage and obstruction of themore » photoexcited charge-carrier motion in the quantum well.« less
  • We have shown that external hydrostatic pressure leads to the creation of structural defects, mainly in the vicinity of the II--VI/GaAs interface in the CdTe/Cd{sub 1-x}Mg{sub x}Te heterostructures grown by the molecular beam epitaxy method on GaAs substrates. These defects propagating across the epilayer cause permanent damage to the samples from the point of view of their electrical properties. In contrast, photoluminescence spectra are only weakly influenced by pressure. Our results shed light on the degradation process observed even without pressure in II--VI-based heterostructures.
  • The relationships between Mg composition, band gap, and lattice characteristics are investigated for Cd 1-xMg xTe barrier layers using a combination of cathodoluminescence, energy dispersive x-ray spectroscopy, variable angle spectral ellipsometry, and atom probe tomography. The use of a simplified, yet accurate, variable angle spectral ellipsometry analysis is shown to be appropriate for fast determination of composition in thin Cd 1-xMg xTe layers. The validity of using high-resolution x-ray diffraction for CdTe/Cd 1-xMg xTe double heterostructures is discussed. Furthermore, the stability of CdTe/Cd 1-xMg xTe heterostructures are investigated with respect to thermal processing.