skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Band alignment of epitaxial ZnS/Zn{sub 3}P{sub 2} heterojunctions

Abstract

The energy-band alignment of epitaxial zb-ZnS(001)/{alpha}-Zn{sub 3}P{sub 2}(001) heterojunctions has been determined by measurement of shifts in the phosphorus 2p and sulfur 2p core-level binding energies for various thicknesses (0.6-2.2 nm) of ZnS grown by molecular beam epitaxy on Zn{sub 3}P{sub 2}. In addition, the position of the valence-band maximum for bulk ZnS and Zn{sub 3}P{sub 2} films was estimated using density functional theory calculations of the valence-band density-of-states. The heterojunction was observed to be type I, with a valence-band offset, {Delta}E{sub V,} of -1.19 {+-} 0.07 eV, which is significantly different from the type II alignment based on electron affinities that is predicted by Anderson theory. n{sup +}-ZnS/p-Zn{sub 3}P{sub 2} heterojunctions demonstrated open-circuit voltages of >750 mV, indicating passivation of the Zn{sub 3}P{sub 2} surface due to the introduction of the ZnS overlayer. Carrier transport across the heterojunction devices was inhibited by the large conduction-band offset, which resulted in short-circuit current densities of <0.1 mA cm{sup -2} under 1 Sun simulated illumination. Hence, constraints on the current density will likely limit the direct application of the ZnS/Zn{sub 3}P{sub 2} heterojunction to photovoltaics, whereas metal-insulator-semiconductor structures that utilize an intrinsic ZnS insulating layer appear promising.

Authors:
; ; ; ;  [1]
  1. Watson Laboratory and Noyes Laboratory, Beckman Institute and Kavli Nanoscience Institute, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States)
Publication Date:
OSTI Identifier:
22089567
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 112; Journal Issue: 9; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BINDING ENERGY; CURRENT DENSITY; DENSITY FUNCTIONAL METHOD; FILMS; HETEROJUNCTIONS; ILLUMINANCE; LAYERS; MOLECULAR BEAM EPITAXY; MOLECULAR STRUCTURE; PHOTOVOLTAIC EFFECT; SEMICONDUCTOR MATERIALS; SIMULATION; SURFACES; THICKNESS; ZINC PHOSPHIDES; ZINC SULFIDES

Citation Formats

Bosco, Jeffrey P., Demers, Steven B., Kimball, Gregory M., Lewis, Nathan S., and Atwater, Harry A. Band alignment of epitaxial ZnS/Zn{sub 3}P{sub 2} heterojunctions. United States: N. p., 2012. Web. doi:10.1063/1.4759280.
Bosco, Jeffrey P., Demers, Steven B., Kimball, Gregory M., Lewis, Nathan S., & Atwater, Harry A. Band alignment of epitaxial ZnS/Zn{sub 3}P{sub 2} heterojunctions. United States. doi:10.1063/1.4759280.
Bosco, Jeffrey P., Demers, Steven B., Kimball, Gregory M., Lewis, Nathan S., and Atwater, Harry A. Thu . "Band alignment of epitaxial ZnS/Zn{sub 3}P{sub 2} heterojunctions". United States. doi:10.1063/1.4759280.
@article{osti_22089567,
title = {Band alignment of epitaxial ZnS/Zn{sub 3}P{sub 2} heterojunctions},
author = {Bosco, Jeffrey P. and Demers, Steven B. and Kimball, Gregory M. and Lewis, Nathan S. and Atwater, Harry A.},
abstractNote = {The energy-band alignment of epitaxial zb-ZnS(001)/{alpha}-Zn{sub 3}P{sub 2}(001) heterojunctions has been determined by measurement of shifts in the phosphorus 2p and sulfur 2p core-level binding energies for various thicknesses (0.6-2.2 nm) of ZnS grown by molecular beam epitaxy on Zn{sub 3}P{sub 2}. In addition, the position of the valence-band maximum for bulk ZnS and Zn{sub 3}P{sub 2} films was estimated using density functional theory calculations of the valence-band density-of-states. The heterojunction was observed to be type I, with a valence-band offset, {Delta}E{sub V,} of -1.19 {+-} 0.07 eV, which is significantly different from the type II alignment based on electron affinities that is predicted by Anderson theory. n{sup +}-ZnS/p-Zn{sub 3}P{sub 2} heterojunctions demonstrated open-circuit voltages of >750 mV, indicating passivation of the Zn{sub 3}P{sub 2} surface due to the introduction of the ZnS overlayer. Carrier transport across the heterojunction devices was inhibited by the large conduction-band offset, which resulted in short-circuit current densities of <0.1 mA cm{sup -2} under 1 Sun simulated illumination. Hence, constraints on the current density will likely limit the direct application of the ZnS/Zn{sub 3}P{sub 2} heterojunction to photovoltaics, whereas metal-insulator-semiconductor structures that utilize an intrinsic ZnS insulating layer appear promising.},
doi = {10.1063/1.4759280},
journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 9,
volume = 112,
place = {United States},
year = {2012},
month = {11}
}