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Title: Impact of extended defects on recombination in CdTe heterostructures grown by molecular beam epitaxy

Abstract

Heterostructures with CdTe and CdTe 1-xSex (x ~ 0.01) absorbers between two wider-band-gap Cd1-xMgxTe barriers (x ~ 0.25-0.3) were grown by molecular beam epitaxy to study carrier generation and recombination in bulk materials with passivated interfaces. Using a combination of confocal photoluminescence (PL), time-resolved PL, and low-temperature PL emission spectroscopy, two extended defect types were identified and the impact of these defects on charge-carrier recombination was analyzed. The dominant defects identified by confocal PL were dislocations in samples grown on (211)B CdTe substrates and crystallographic twinning-related defects in samples on (100)-oriented InSb substrates. Low-temperature PL shows that twin-related defects have a zero-phonon energy of 1.460 eV and a Huang-Rhys factor of 1.50, while dislocation-dominated samples have a 1.473-eV zero-phonon energy and a Huang-Rhys factor of 1.22. The charge carrier diffusion length near both types of defects is ~6 um, suggesting that recombination is limited by diffusion dynamics. For heterostructures with a low concentration of extended defects, the bulk lifetime was determined to be 2.2 us with an interface recombination velocity of 160 cm/s and an estimated radiative lifetime of 91 us.

Authors:
 [1]; ORCiD logo [2];  [3];  [2];  [3]; ORCiD logo [3]; ORCiD logo [3];  [3]; ORCiD logo [3];  [3];  [2]; ORCiD logo [3]
  1. Department of Physics, Colorado State University, Fort Collins, Colorado 80523, USA; National Renewable Energy Laboratory, Golden, Colorado 80401, USA
  2. National Renewable Energy Laboratory, Golden, Colorado 80401, USA
  3. Materials Science, Engineering and Commercialization Program, Texas State University, San Marcos, Texas 78666, USA
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:
1326171
Report Number(s):
NREL/JA-5K00-67149
Journal ID: ISSN 0003-6951
DOE Contract Number:
AC36-08GO28308
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 9
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; photoluminescence; epitaxy; II-VI semiconductors; diffusion; III-V semiconductors

Citation Formats

Zaunbrecher, Katherine N., Kuciauskas, Darius, Swartz, Craig H., Dippo, Pat, Edirisooriya, Madhavie, Ogedengbe, Olanrewaju S., Sohal, Sandeep, Hancock, Bobby L., LeBlanc, Elizabeth G., Jayathilaka, Pathiraja A. R. D., Barnes, Teresa M., and Myers, Thomas H.. Impact of extended defects on recombination in CdTe heterostructures grown by molecular beam epitaxy. United States: N. p., 2016. Web. doi:10.1063/1.4961989.
Zaunbrecher, Katherine N., Kuciauskas, Darius, Swartz, Craig H., Dippo, Pat, Edirisooriya, Madhavie, Ogedengbe, Olanrewaju S., Sohal, Sandeep, Hancock, Bobby L., LeBlanc, Elizabeth G., Jayathilaka, Pathiraja A. R. D., Barnes, Teresa M., & Myers, Thomas H.. Impact of extended defects on recombination in CdTe heterostructures grown by molecular beam epitaxy. United States. doi:10.1063/1.4961989.
Zaunbrecher, Katherine N., Kuciauskas, Darius, Swartz, Craig H., Dippo, Pat, Edirisooriya, Madhavie, Ogedengbe, Olanrewaju S., Sohal, Sandeep, Hancock, Bobby L., LeBlanc, Elizabeth G., Jayathilaka, Pathiraja A. R. D., Barnes, Teresa M., and Myers, Thomas H.. 2016. "Impact of extended defects on recombination in CdTe heterostructures grown by molecular beam epitaxy". United States. doi:10.1063/1.4961989.
@article{osti_1326171,
title = {Impact of extended defects on recombination in CdTe heterostructures grown by molecular beam epitaxy},
author = {Zaunbrecher, Katherine N. and Kuciauskas, Darius and Swartz, Craig H. and Dippo, Pat and Edirisooriya, Madhavie and Ogedengbe, Olanrewaju S. and Sohal, Sandeep and Hancock, Bobby L. and LeBlanc, Elizabeth G. and Jayathilaka, Pathiraja A. R. D. and Barnes, Teresa M. and Myers, Thomas H.},
abstractNote = {Heterostructures with CdTe and CdTe 1-xSex (x ~ 0.01) absorbers between two wider-band-gap Cd1-xMgxTe barriers (x ~ 0.25-0.3) were grown by molecular beam epitaxy to study carrier generation and recombination in bulk materials with passivated interfaces. Using a combination of confocal photoluminescence (PL), time-resolved PL, and low-temperature PL emission spectroscopy, two extended defect types were identified and the impact of these defects on charge-carrier recombination was analyzed. The dominant defects identified by confocal PL were dislocations in samples grown on (211)B CdTe substrates and crystallographic twinning-related defects in samples on (100)-oriented InSb substrates. Low-temperature PL shows that twin-related defects have a zero-phonon energy of 1.460 eV and a Huang-Rhys factor of 1.50, while dislocation-dominated samples have a 1.473-eV zero-phonon energy and a Huang-Rhys factor of 1.22. The charge carrier diffusion length near both types of defects is ~6 um, suggesting that recombination is limited by diffusion dynamics. For heterostructures with a low concentration of extended defects, the bulk lifetime was determined to be 2.2 us with an interface recombination velocity of 160 cm/s and an estimated radiative lifetime of 91 us.},
doi = {10.1063/1.4961989},
journal = {Applied Physics Letters},
number = 9,
volume = 109,
place = {United States},
year = 2016,
month = 8
}
  • Cited by 4
  • Heterostructures with CdTe and CdTe{sub 1-x}Se{sub x} (x ∼ 0.01) absorbers between two wider-band-gap Cd{sub 1-x}Mg{sub x}Te barriers (x ∼ 0.25–0.3) were grown by molecular beam epitaxy to study carrier generation and recombination in bulk materials with passivated interfaces. Using a combination of confocal photoluminescence (PL), time-resolved PL, and low-temperature PL emission spectroscopy, two extended defect types were identified and the impact of these defects on charge-carrier recombination was analyzed. The dominant defects identified by confocal PL were dislocations in samples grown on (211)B CdTe substrates and crystallographic twinning-related defects in samples on (100)-oriented InSb substrates. Low-temperature PL shows that twin-related defects have amore » zero-phonon energy of 1.460 eV and a Huang-Rhys factor of 1.50, while dislocation-dominated samples have a 1.473-eV zero-phonon energy and a Huang-Rhys factor of 1.22. The charge carrier diffusion length near both types of defects is ∼6 μm, suggesting that recombination is limited by diffusion dynamics. For heterostructures with a low concentration of extended defects, the bulk lifetime was determined to be 2.2 μs with an interface recombination velocity of 160 cm/s and an estimated radiative lifetime of 91 μs.« less
  • The bulk Shockley-Read-Hall carrier lifetime of CdTe and interface recombination velocity at the CdTe/Mg{sub 0.24}Cd{sub 0.76}Te heterointerface are estimated to be around 0.5 μs and (4.7 ± 0.4) × 10{sup 2 }cm/s, respectively, using time-resolved photoluminescence (PL) measurements. Four CdTe/MgCdTe double heterostructures (DHs) with varying CdTe layer thicknesses were grown on nearly lattice-matched InSb (001) substrates using molecular beam epitaxy. The longest lifetime of 179 ns is observed in the DH with a 2 μm thick CdTe layer. It is also shown that the photon recycling effect has a strong influence on the bulk radiative lifetime, and the reabsorption process affects the measured PL spectrum shape and intensity.
  • The interface recombination velocities of CdTe/Mg{sub x}Cd{sub 1−x}Te double heterostructure (DH) samples with different CdTe layer thicknesses and Mg compositions are studied using time-resolved photoluminescence measurements. A lowest interface recombination velocity of 30 ± 10 cm/s has been measured for the CdTe/Mg{sub 0.46}Cd{sub 0.54}Te interface, and a longest carrier lifetime of 0.83 μs has been observed for the studied DHs. These values are very close to the best reported numbers for GaAs/AlGaAs DHs. The impact of carrier escape through thermionic emission over the MgCdTe barrier on the recombination process in the DHs is also studied.
  • 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.