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Title: Effects of excess carriers on charged defect concentrations in wide bandgap semiconductors

Unintentional doping and doping limits in semiconductors are typically caused by compensating defects with low formation energies. Since the formation enthalpy of a charged defect depends linearly on the Fermi level, doping limits can be especially pronounced in wide bandgap semiconductors where the Fermi level can vary substantially. Introduction of non-equilibrium carrier concentrations during growth or processing alters the chemical potentials of band carriers and allows populations of charged defects to be modified in ways impossible at thermal equilibrium. We demonstrate that in the presence of excess carriers, the rates of carrier capture and emission involving a defect charge transition level determine the admixture of electron and hole quasi-Fermi levels involved in the formation enthalpy of non-zero charge defect states. To understand the range of possible responses, we investigate the behavior of a single donor-like defect as functions of extrinsic doping and charge transition level energy. We find that that excess carriers will increase the formation enthalpy of compensating defects for most values of the charge transition level in the bandgap. Thus, it may be possible to use non-equilibrium carrier concentrations to overcome limitations on doping imposed by native defects. Cases also exist in which the concentration of defects withmore » the same charge polarity as the majority dopant is either left unchanged or actually increases. This surprising effect arises when emission rates are suppressed relative to the capture rates and is most pronounced in wide bandgap semiconductors. We provide guidelines for carrying out experimental tests of this model.« less
Authors:
 [1] ; ORCiD logo [2]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. Univ. of Utah, Salt Lake City, UT (United States)
Publication Date:
Report Number(s):
NREL/JA-5K00-71463
Journal ID: ISSN 0021-8979
Grant/Contract Number:
AC36-08GO28308; EE0004946
Type:
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 123; Journal Issue: 18; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; thermodynamics; thermodynamic functions; doping; band gap; band structure; semiconductors; surface collisions; epitaxy; crystal defects
OSTI Identifier:
1440312
Alternate Identifier(s):
OSTI ID: 1436390

Alberi, Kirstin, and Scarpulla, Michael A. Effects of excess carriers on charged defect concentrations in wide bandgap semiconductors. United States: N. p., Web. doi:10.1063/1.5010945.
Alberi, Kirstin, & Scarpulla, Michael A. Effects of excess carriers on charged defect concentrations in wide bandgap semiconductors. United States. doi:10.1063/1.5010945.
Alberi, Kirstin, and Scarpulla, Michael A. 2018. "Effects of excess carriers on charged defect concentrations in wide bandgap semiconductors". United States. doi:10.1063/1.5010945.
@article{osti_1440312,
title = {Effects of excess carriers on charged defect concentrations in wide bandgap semiconductors},
author = {Alberi, Kirstin and Scarpulla, Michael A.},
abstractNote = {Unintentional doping and doping limits in semiconductors are typically caused by compensating defects with low formation energies. Since the formation enthalpy of a charged defect depends linearly on the Fermi level, doping limits can be especially pronounced in wide bandgap semiconductors where the Fermi level can vary substantially. Introduction of non-equilibrium carrier concentrations during growth or processing alters the chemical potentials of band carriers and allows populations of charged defects to be modified in ways impossible at thermal equilibrium. We demonstrate that in the presence of excess carriers, the rates of carrier capture and emission involving a defect charge transition level determine the admixture of electron and hole quasi-Fermi levels involved in the formation enthalpy of non-zero charge defect states. To understand the range of possible responses, we investigate the behavior of a single donor-like defect as functions of extrinsic doping and charge transition level energy. We find that that excess carriers will increase the formation enthalpy of compensating defects for most values of the charge transition level in the bandgap. Thus, it may be possible to use non-equilibrium carrier concentrations to overcome limitations on doping imposed by native defects. Cases also exist in which the concentration of defects with the same charge polarity as the majority dopant is either left unchanged or actually increases. This surprising effect arises when emission rates are suppressed relative to the capture rates and is most pronounced in wide bandgap semiconductors. We provide guidelines for carrying out experimental tests of this model.},
doi = {10.1063/1.5010945},
journal = {Journal of Applied Physics},
number = 18,
volume = 123,
place = {United States},
year = {2018},
month = {5}
}