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Title: Self-compensation in arsenic doping of CdTe

Abstract

Efficient p-type doping in CdTe has remained a critical challenge for decades, limiting the performance of CdTe-based semiconductor devices. Arsenic is a promising p-type dopant; however, reproducible doping with high concentration is difficult and carrier lifetime is low. We systematically studied defect structures in As-doped CdTe using high-purity single crystal wafers to investigate the mechanisms that limit p-type doping. Two As-doped CdTe with varying acceptor density and two undoped CdTe were grown in Cd-rich and Te-rich environments. The defect structures were investigated by thermoelectric-effect spectroscopy (TEES), and first-principles calculations were used for identifying and assigning the experimentally observed defects. Measurements revealed activation of As is very low in both As-doped samples with very short lifetimes indicating strong compensation and the presence of significant carrier trapping defects. Defect studies suggest two acceptors and one donor level were introduced by As doping with activation energies at ~88 meV, ~293 meV and ~377 meV. In particular, the peak shown at ~162 K in the TEES spectra is very prominent in both As-doped samples, indicating a signature of AX-center donors. In conclusion, the AX-centers are believed to be responsible for most of the compensation because of their low formation energy and very prominent peakmore » intensity in TEES spectra.« less

Authors:
ORCiD logo [1];  [2];  [3];  [4];  [4];  [4];  [4];  [5]; ORCiD logo [2]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States); Washington State Univ., Pullman, WA (United States)
  2. Washington State Univ., Pullman, WA (United States)
  3. Soochow Univ., Suzhou (China)
  4. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  5. Beijing Computational Science Research Center, Beijing (China)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
OSTI Identifier:
1372626
Report Number(s):
NREL/JA-5K00-68633
Journal ID: ISSN 2045-2322
Grant/Contract Number:
AC36-08GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; doping; CdTe; compensation; arsenic

Citation Formats

Ablekim, Tursun, Swain, Santosh K., Yin, Wan -Jian, Zaunbrecher, Katherine, Burst, James, Barnes, Teresa M., Kuciauskas, Darius, Wei, Su -Huai, and Lynn, Kelvin G. Self-compensation in arsenic doping of CdTe. United States: N. p., 2017. Web. doi:10.1038/s41598-017-04719-0.
Ablekim, Tursun, Swain, Santosh K., Yin, Wan -Jian, Zaunbrecher, Katherine, Burst, James, Barnes, Teresa M., Kuciauskas, Darius, Wei, Su -Huai, & Lynn, Kelvin G. Self-compensation in arsenic doping of CdTe. United States. doi:10.1038/s41598-017-04719-0.
Ablekim, Tursun, Swain, Santosh K., Yin, Wan -Jian, Zaunbrecher, Katherine, Burst, James, Barnes, Teresa M., Kuciauskas, Darius, Wei, Su -Huai, and Lynn, Kelvin G. Tue . "Self-compensation in arsenic doping of CdTe". United States. doi:10.1038/s41598-017-04719-0. https://www.osti.gov/servlets/purl/1372626.
@article{osti_1372626,
title = {Self-compensation in arsenic doping of CdTe},
author = {Ablekim, Tursun and Swain, Santosh K. and Yin, Wan -Jian and Zaunbrecher, Katherine and Burst, James and Barnes, Teresa M. and Kuciauskas, Darius and Wei, Su -Huai and Lynn, Kelvin G.},
abstractNote = {Efficient p-type doping in CdTe has remained a critical challenge for decades, limiting the performance of CdTe-based semiconductor devices. Arsenic is a promising p-type dopant; however, reproducible doping with high concentration is difficult and carrier lifetime is low. We systematically studied defect structures in As-doped CdTe using high-purity single crystal wafers to investigate the mechanisms that limit p-type doping. Two As-doped CdTe with varying acceptor density and two undoped CdTe were grown in Cd-rich and Te-rich environments. The defect structures were investigated by thermoelectric-effect spectroscopy (TEES), and first-principles calculations were used for identifying and assigning the experimentally observed defects. Measurements revealed activation of As is very low in both As-doped samples with very short lifetimes indicating strong compensation and the presence of significant carrier trapping defects. Defect studies suggest two acceptors and one donor level were introduced by As doping with activation energies at ~88 meV, ~293 meV and ~377 meV. In particular, the peak shown at ~162 K in the TEES spectra is very prominent in both As-doped samples, indicating a signature of AX-center donors. In conclusion, the AX-centers are believed to be responsible for most of the compensation because of their low formation energy and very prominent peak intensity in TEES spectra.},
doi = {10.1038/s41598-017-04719-0},
journal = {Scientific Reports},
number = 1,
volume = 7,
place = {United States},
year = {Tue Jul 04 00:00:00 EDT 2017},
month = {Tue Jul 04 00:00:00 EDT 2017}
}

Journal Article:
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  • Cd-rich composition and group-V element doping are of interest for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe, but the critical details concerning point defects are not yet fully established. Herein, we report on the properties of arsenic doped CdTe single crystals grown from Cd solvent by the travelling heater method. The photoluminescence spectra and activation energy of 74 +/- 2 meV derived from the temperature-dependent Hall effect are consistent with AsTe as the dominant acceptor. Doping in the 10^16 to 10^17/cm^3 range is achieved for measured As concentrations between 10^16 and 10^20/cm^3 with the highest dopingmore » efficiency of 40% occurring near 10^17 As/cm^3. We observe persistent photoconductivity, a hallmark of light-induced metastable configuration changes consistent with AX behavior. Additionally, quenching experiments reveal at least two mechanisms of increased p-type doping in the dark, one decaying over 2-3 weeks and the other persisting for at least 2 months. These results provide essential insights for the application of As-doped CdTe in thin film solar cells.« less
  • Here, Group-V element doping is promising for simultaneously maximizing the hole concentration and minority carrier lifetime in CdTe for thin film solar cells, but there are roadblocks concerning point defects including the possibility of self-compensation by AX metastability. Herein, we report on doping, lifetime, and mobility of CdTe single crystals doped with As between 10 16 and 10 20 cm –3 grown from the Cd solvent by the travelling heater method. Evidence consistent with AX instability as a major contributor to compensation in samples doped below 10 17 cm –3 is presented, while for higher-doped samples, precipitation of a secondmore » phase on planar structural defects is also observed and may explain spatial variation in properties such as lifetime. Rapid cooling after crystal growth increases doping efficiency and mobility for times up to 20–30 days at room temperature with the highest efficiencies observed close to 45% and a hole mobility of 70 cm 2/Vs at room temperature. A doping limit in the low 10 17/cm 3 range is observed for samples quenched at 200–300 °C/h. Bulk minority carrier lifetimes exceeding 20 ns are observed for samples doped near 10 16 cm –3 relaxed in the dark and for unintentionally doped samples, while a lifetime of nearly 5 ns is observed for 10 18 cm –3 As doping. These results help us to establish limits on properties expected for group-V doped CdTe polycrystalline thin films for use in photovoltaics.« less