Issue 9, 2016

Calculation of dopant solubilities and phase diagrams of X–Pb–Se (X = Br, Na) limited to defects with localized charge

Abstract

The control of defects, particularly impurities, to tune the concentrations of electrons and holes is of utmost importance in the use of semiconductor materials. To estimate the amount of dopant that can be added to a semiconductor without precipitating secondary phases, a detailed phase diagram is needed. The ability of ab initio computational methods to predict defect stability can greatly accelerate the discovery of new semiconductors by calculating phase diagrams when time-consuming experimental ones are not available. DFT defect energy calculations are particularly successful in identifying doping strategies by determining the energy of multiple defect charge states in large band gap semiconductors and insulators. In metals, detailed phase diagrams can be determined from such calculations but only one, uncharged defect is needed. In this work, we have calculated dopant solubilities of Br and Na in the thermoelectric material PbSe by mapping its solvus boundaries in different regions of the respective ternary phase diagrams using DFT defect energy calculations. The narrow gap PbSe provides an example where defects with nominal charge state (based on valence counting) have properly-localized charge states. However, defects with unexpected charge states produce delocalized electrons, which are then, in effect, defects with the expected charge state. Simply applying the methods for calculating multiple defect charge states in PbSe and treating them as separate defects fails to predict properties measured by experiments. Performing thermodynamic calculations using only the expected charge states, excluding others, enables accurate prediction of experimentally measured doping efficiencies and phase diagrams. Identifying which defect charge states to include in thermodynamic calculations will expedite the use of such calculations for other semiconductors in understanding phase diagrams and devising effective doping strategies.

Graphical abstract: Calculation of dopant solubilities and phase diagrams of X–Pb–Se (X = Br, Na) limited to defects with localized charge

Article information

Article type
Communication
Submitted
25 十一月 2015
Accepted
08 二月 2016
First published
09 二月 2016

J. Mater. Chem. C, 2016,4, 1769-1775

Calculation of dopant solubilities and phase diagrams of X–Pb–Se (X = Br, Na) limited to defects with localized charge

S. Bajaj, H. Wang, J. W. Doak, C. Wolverton and G. Jeffrey Snyder, J. Mater. Chem. C, 2016, 4, 1769 DOI: 10.1039/C5TC03970C

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements