Title: Surface photovoltage spectroscopy observes junctions and carrier separation in gallium nitride nanowire arrays for overall water-splitting

Abstract

Gallium nitride (GaN) nanowire arrays on silicon are able to drive the overall water-splitting reaction with up to 3.3% solar-to-hydrogen efficiency. Photochemical charge separation is key to the operation of these devices, but details are difficult to observe experimentally because of the number of components and interfaces. Here, we use surface photovoltage spectroscopy to study charge transfer in i-, n-, and p-GaN nanowire arrays on n+ -Si wafers in the presence and absence of Rh/Cr₂O₃ co-catalysts. The effect of the space charge layer and sub-bandgap defects on majority and minority carrier transport can be clearly observed, and estimates of the built-in potential of the junctions can be made. Transient illumination of the p-GaN/n⁺-Si junction generates up to -1.4 V surface photovoltage by carrier separation along the GaN nanowire axis. This process is central to the overall water-splitting function of the n⁺-Si/p-GaN/Rh/Cr₂O₃ nanowire array. Overall, these results improve our understanding of photochemical charge transfer and separation in group III–V semiconductor nanostructures for the conversion of solar energy into fuels.

Authors:

Doughty, Rachel M.  ^[1];

• Search DOE PAGES for author "Doughty, Rachel M."
• Search DOE PAGES for ORCID "0000-0002-7306-6014"

Chowdhury, Faqrul A.  ^[2];

• Search DOE PAGES for author "Chowdhury, Faqrul A."
• Search DOE PAGES for ORCID "0000-0001-9747-5368"

Mi, Zetian  ^[3];

• Search DOE PAGES for author "Mi, Zetian"
• Search DOE PAGES for ORCID "0000-0001-9494-7390"

Osterloh, Frank E.  ^[1]

• Search DOE PAGES for author "Osterloh, Frank E."
• Search DOE PAGES for ORCID "0000-0002-9288-3407"

---

+ Show Author Affiliations

1. Univ. of California, Davis, CA (United States). Dept. of Chemistry
2. McGill Univ., Montreal, QC (Canada). Dept of Physics; McGill Univ., Montreal, QC (Canada). Dept of Electrical and Computer Engineering
3. McGill Univ., Montreal, QC (Canada). Dept of Electrical and Computer Engineering; Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Electrical Engineering and Computer Science

Publication Date:

Wed Oct 14 00:00:00 EDT 2020

Research Org.:

Univ. of California, Davis, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)

OSTI Identifier:

1851987

Alternate Identifier(s):

OSTI ID: 1671855

Grant/Contract Number:  

SC0015329; CBET 1804458

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Chemical Physics

Additional Journal Information:

Journal Volume: 153; Journal Issue: 14; Journal ID: ISSN 0021-9606

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Chemistry; physics; semiconductor device fabrication; photovoltaics; solar energy; semiconductor nanostructures; nanowires; catalysts and catalysis; epitaxy; water-splitting; spectroscopy