Title: Monte Carlo simulations of disorder in $\mathrm{ZnSn}{\mathrm{N}}_2$ and the effects on the electronic structure

Abstract

In multinary compound semiconductors, cation disorder can decisively alter the electronic properties and impact potential applications. ZnSnN₂ is a ternary nitride of interest for photovoltaics, which forms in a wurtzite-derived crystal structure. In the ground state, every N anion is coordinated by two Zn and two Sn cations, thereby observing the octet rule locally. Using a motif-based model Hamiltonian, we performed Monte Carlo simulations that provide atomistic representations of ZnSnN₂ with varying degrees of cation disorder. Subsequent electronic structure calculations describe the evolution of band gaps, optical properties, and carrier localization effects as a function of the disorder. We find that octet-rule conserving disorder is practically impossible to avoid but perfectly benign, with hardly any effects on the electronic structure. In contrast, a fully random cation distribution would be very detrimental, but fortunately it is energetically highly unfavorable. A degree of disorder that can realistically be expected for nonequilibrium thin-film deposition leads to a moderate band-gap reduction and to moderate carrier localization effects. Comparing the simulated structures with experimental samples grown by sputtering, we find evidence that these samples indeed incorporate a certain degree of octet-rule violating disorder, which is reflected in the x-ray diffraction and in the optical absorptionmore » spectra. This study demonstrates that the electronic properties of ZnSnN₂ are dominated by changes of the local coordination environments rather than long-range ordering effects.« less

Authors:

Lany, Stephan ^[1]; Fioretti, Angela N. ^[2]; Zawadzki, Paweł P. ^[1]; Schelhas, Laura T. ^[3]; Toberer, Eric S. ^[2]; Zakutayev, Andriy ^[1]; Tamboli, Adele C. ^[2]

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+ Show Author Affiliations

1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
2. National Renewable Energy Lab. (NREL), Golden, CO (United States); Colorado School of Mines, Golden, CO (United States)
3. SLAC National Accelerator Lab., Menlo Park, CA (United States)

Publication Date:

Thu Aug 10 00:00:00 EDT 2017

Research Org.:

National Renewable Energy Lab. (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE); USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1415121

Alternate Identifier(s):

OSTI ID: 1374771

Report Number(s):

NREL/JA-5K00-68918
Journal ID: ISSN 2475-9953; PRMHAR; TRN: US1800756

Grant/Contract Number:  

AC36-08GO28308; AC02-76SF00515

Resource Type:

Journal Article: Accepted Manuscript

Journal Name:

Physical Review Materials

Additional Journal Information:

Journal Volume: 1; Journal Issue: 3; Journal ID: ISSN 2475-9953

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

14 SOLAR ENERGY; 36 MATERIALS SCIENCE; photovoltaics; electronic structure; Monte Carlo simulation