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Title: Majority Carrier Properties of Single Crystal Cu 2− x ZnSnSe 4 with Varying Copper Composition

Abstract

The dependence of carrier concentration on copper content in Cu 2− x ZnSnSe 4 single crystals, grown without fluxing agents, is presented over the composition range Cu/(Zn + Sn) of 0.77–0.93 and Zn/Sn from 1.3 (low Cu content) to 1.3 (high Cu content). Single phase mono‐crystals with facets up to 5 mm are synthesized from high‐purity elements and validated using Laue diffraction. A direct optical band gap of 0.98 eV is observed for a crystal with Cu/(Zn + Sn) = 0.85. Van der Pauw–Hall resistance analysis shows decreasing hole concentration, from 10 19  cm −3 to 2 × 10 15  cm −3 , with decreasing copper content over the composition range. Hole mobility varies from 50 cm 2  V −1  s −1 to 160 cm 2  V −1  s −1 , with no dependence on copper concentration. A linear temperature dependence of the Seebeck coefficient is found for all crystals. The Seebeck coefficient–carrier concentration dependence is used to determine the valence band density of states, N V , and corresponding effective mass, μ h *. Crystals with Cu/(Zn + Sn) < 0.9 have N V  = 4 × 10 18  cm −3 and μ h * = 0.4 m 0 while crystals with elevated copper concentration, Cu/(Zn + Sn) > 0.9, exhibit higher density of states, N V  = 3 × 10 19  cmmore » −3 and hole effective mass μ h * = 0.9 m 0 . The increased valence band density of states at elevated copper composition is consistent with more Cu–Zn exchange sites contributing to bulk defects and band edge fluctuations. Temperature‐dependent conductivity measurements indicate a transition from metallic‐type to semiconductor‐type conduction at Cu/(Zn + Sn) < 0.9. At lower copper content, for a crystal with Cu/(Zn + Sn) = 0.83 and p  = 10 17  cm −3 the activation energy for intrinsic conduction is 60 meV. This behavior is attributed to the copper vacancy defect, V Cu , and is comparable to reported values obtained in thin films and by first‐principles predictions.« less

Authors:
ORCiD logo [1];  [2];  [1]
  1. Institute of Energy Conversion University of Delaware 451 Wyoming Road Newark DE 19716 USA
  2. IBM TJ Watson Research Center 1101 Kitchawan Rd Yorktown Heights NY 10598 USA
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1542679
Grant/Contract Number:  
DE‐EE0006334
Resource Type:
Publisher's Accepted Manuscript
Journal Name:
Physica Status Solidi B. Basic Solid State Physics
Additional Journal Information:
Journal Name: Physica Status Solidi B. Basic Solid State Physics Journal Volume: 256 Journal Issue: 11; Journal ID: ISSN 0370-1972
Publisher:
Wiley Blackwell (John Wiley & Sons)
Country of Publication:
Germany
Language:
English

Citation Formats

McCandless, Brian E., Bishop, Doug, and Lloyd, Michael. Majority Carrier Properties of Single Crystal Cu 2− x ZnSnSe 4 with Varying Copper Composition. Germany: N. p., 2019. Web. doi:10.1002/pssb.201900180.
McCandless, Brian E., Bishop, Doug, & Lloyd, Michael. Majority Carrier Properties of Single Crystal Cu 2− x ZnSnSe 4 with Varying Copper Composition. Germany. https://doi.org/10.1002/pssb.201900180
McCandless, Brian E., Bishop, Doug, and Lloyd, Michael. Tue . "Majority Carrier Properties of Single Crystal Cu 2− x ZnSnSe 4 with Varying Copper Composition". Germany. https://doi.org/10.1002/pssb.201900180.
@article{osti_1542679,
title = {Majority Carrier Properties of Single Crystal Cu 2− x ZnSnSe 4 with Varying Copper Composition},
author = {McCandless, Brian E. and Bishop, Doug and Lloyd, Michael},
abstractNote = {The dependence of carrier concentration on copper content in Cu 2− x ZnSnSe 4 single crystals, grown without fluxing agents, is presented over the composition range Cu/(Zn + Sn) of 0.77–0.93 and Zn/Sn from 1.3 (low Cu content) to 1.3 (high Cu content). Single phase mono‐crystals with facets up to 5 mm are synthesized from high‐purity elements and validated using Laue diffraction. A direct optical band gap of 0.98 eV is observed for a crystal with Cu/(Zn + Sn) = 0.85. Van der Pauw–Hall resistance analysis shows decreasing hole concentration, from 10 19  cm −3 to 2 × 10 15  cm −3 , with decreasing copper content over the composition range. Hole mobility varies from 50 cm 2  V −1  s −1 to 160 cm 2  V −1  s −1 , with no dependence on copper concentration. A linear temperature dependence of the Seebeck coefficient is found for all crystals. The Seebeck coefficient–carrier concentration dependence is used to determine the valence band density of states, N V , and corresponding effective mass, μ h *. Crystals with Cu/(Zn + Sn) < 0.9 have N V  = 4 × 10 18  cm −3 and μ h * = 0.4 m 0 while crystals with elevated copper concentration, Cu/(Zn + Sn) > 0.9, exhibit higher density of states, N V  = 3 × 10 19  cm −3 and hole effective mass μ h * = 0.9 m 0 . The increased valence band density of states at elevated copper composition is consistent with more Cu–Zn exchange sites contributing to bulk defects and band edge fluctuations. Temperature‐dependent conductivity measurements indicate a transition from metallic‐type to semiconductor‐type conduction at Cu/(Zn + Sn) < 0.9. At lower copper content, for a crystal with Cu/(Zn + Sn) = 0.83 and p  = 10 17  cm −3 the activation energy for intrinsic conduction is 60 meV. This behavior is attributed to the copper vacancy defect, V Cu , and is comparable to reported values obtained in thin films and by first‐principles predictions.},
doi = {10.1002/pssb.201900180},
journal = {Physica Status Solidi B. Basic Solid State Physics},
number = 11,
volume = 256,
place = {Germany},
year = {2019},
month = {7}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
https://doi.org/10.1002/pssb.201900180

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Cited by: 2 works
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Works referenced in this record:

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