Nanoscale fissure formation in AlxGa1–xN/GaN heterostructures and their influence on Ohmic contact formation

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Smith, M. D. and Thomson, D. and Zubialevich, V. Z. and Li, H. and Naresh-Kumar, G. and Trager-Cowan, C. and Parbrook, P. J. (2017) Nanoscale fissure formation in AlxGa1–xN/GaN heterostructures and their influence on Ohmic contact formation. Physica Status Solidi A, 214 (1). 1600353. ISSN 1862-6300 (https://doi.org/10.1002/pssa.201600353)

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Abstract

Nanoscale surface fissures on AlxGa1–xN/GaN (15 nm/1 µm) heterostructures grown by metalorganic vapour phase epitaxy (MOVPE) were imaged using tapping-mode atomic force microscopy (AFM) and electron channelling contrast imaging (ECCI). Fissure formation was linked to threading dislocations, and was only observed in samples cooled under H2 and NH3, developing with increasing barrier layer Al content. No strain relaxation was detected regardless of fissure formation up to barrier layer Al composition fractions of x = 0.37. A reduction of measured channel carrier density was found in fissured samples at low temperature. This instability is attributed to shallow trap formation associated with fissure boundaries. For Ti/Al/Ni/Au Ohmic contact formation to high Al content barrier layers, fissures were found to offer conduction routes to the 2DEG that allow for low resistance contacts, with fissure-free samples requiring additional optimisation of the metal stack and anneal conditions to achieve contact resistivity of order those measured in fissured samples. In addition, the effects of fissures were found to be detrimental to thermal stability of sheet and contact resistance, suggesting that fissure formation compromises the integrity of the 2DEG.

ORCID iDs

Smith, M. D., Thomson, D. ORCID logoORCID: https://orcid.org/0000-0003-4900-5307, Zubialevich, V. Z., Li, H., Naresh-Kumar, G. ORCID logoORCID: https://orcid.org/0000-0002-9642-8137, Trager-Cowan, C. ORCID logoORCID: https://orcid.org/0000-0001-8684-7410 and Parbrook, P. J.;
  • Item type:Article
    ID code:59478
    Dates:
    Date
    Event
    31 January 2017
    Published
    25 October 2016
    Published Online
    30 September 2016
    Accepted
    Notes:This is the peer reviewed version of the following article: Smith, M. D., Thomson, D., Zubialevich, V. Z., Li, H., Naresh-Kumar, G., Trager-Cowan, C., & Parbrook, P. J. (2017). Nanoscale fissure formation in AlxGa1–xN/GaN heterostructures and their influence on Ohmic contact formation. Physica Status Solidi A, [1600353]. , which has been published in final form at https://doi.org/10.1002/pssa.201600353. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
    Subjects:Science > Physics
    Department:Faculty of Science > Physics
    Technology and Innovation Centre > Photonics
    Depositing user: Pure Administrator
    Date deposited:18 Jan 2017 12:39
    Last modified:14 Dec 2024 13:24
    URI:https://strathprints.strath.ac.uk/id/eprint/59478
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