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  Mechanism leading to semi-insulating property of carbon-doped GaN: Analysis of donor acceptor ratio and method for its determination

Koller, C. M., Lymperakis, L., Pogany, D., Pobegen, G., & Ostermaier, C. (2021). Mechanism leading to semi-insulating property of carbon-doped GaN: Analysis of donor acceptor ratio and method for its determination. Journal of Applied Physics, 130(18): 185702. doi:10.1063/5.0060912.

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 Creators:
Koller, Christian Martin1, Author           
Lymperakis, L.2, Author           
Pogany, D.3, Author
Pobegen, G.1, Author
Ostermaier, C.4, Author
Affiliations:
1KAI GmbH, Europastraße 8, 9524 Villach, Austria, ou_persistent22              
2Microstructure, Computational Materials Design, Max-Planck-Institut für Eisenforschung GmbH, Max Planck Society, ou_1863344              
3Institute of Solid State Electronics, TU Wien, Gußhausstraße 25a, 1040 Vienna, Austria, ou_persistent22              
4Infineon Technologies Austria AG, Siemensstraße 2, 9500 Villach, Austria, ou_persistent22              

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 Abstract: Carbon impurities in GaN form both acceptors and donors. Donor-to-acceptor ratios (DARs) determine the semi-insulating behavior of carbon-doped GaN (GaN:C) layers and are still debated. Two models are discussed; both can theoretically achieve semi-insulating behavior: the dominant acceptor model (DAM, DAR<1) and the auto-compensation model (ACM, DAR=1). We perform a capacitance–voltage analysis on metal/GaN:C/nGaN (n-doped GaN) structures, exhibiting Fermi-level pinning in GaN:C, 0.7 eV above the valence band maximum. This observation coupled with further interpretation clearly supports the DAM and contradicts the ACM. Furthermore, we reveal a finite depletion width of a transition region in GaN:C next to nGaN, where carbon acceptors drop below the Fermi level becoming fully ionized. Calculation of the potential drop in this region exhibits DAR values of 0.5–0.67 for GaN:C with total carbon concentrations of 1018 cm−3 and 1019 cm−3. Based on those results, we re-evaluate formerly published density functional theory (DFT)-calculated formation energies of point defects in GaN. Unexpectedly, growth in thermodynamic equilibrium with the bulk carbon phase contradicts our experimental analysis. Therefore, we propose the consideration of extreme carbon-rich growth conditions. As bulk carbon and carbon cluster formation are not reported to date, we consider a metastable GaN:C solid solution with the competing carbon bulk phase being kinetically hindered. DFT and experimental results agree, confirming the role of carbon at nitrogen sites as dominant acceptors. Under N-rich conditions, carbon at gallium sites is the dominant donor, whereas additional nitrogen vacancies are generated under Ga-rich conditions.

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Language(s): eng - English
 Dates: 2021-11-092021-11
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1063/5.0060912
 Degree: -

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Title: Journal of Applied Physics
  Abbreviation : J. Appl. Phys.
Source Genre: Journal
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Publ. Info: New York, NY : AIP Publishing
Pages: 11 Volume / Issue: 130 (18) Sequence Number: 185702 Start / End Page: - Identifier: ISSN: 0021-8979
CoNE: https://pure.mpg.de/cone/journals/resource/991042723401880