Thermal stress modelling of diamond on GaN/III-Nitride membranes

Cuenca, Jerome A. and Smith, Matthew D. and Field, Daniel E. and Massabuau, Fabien C-P. and Mandal, Soumen and Pomeroy, James and Wallis, David J. and Oliver, Rachel A. and Thayne, Iain and Kuball, Martin and Williams, Oliver A. (2020) Thermal stress modelling of diamond on GaN/III-Nitride membranes. Carbon. ISSN 0008-6223 (https://doi.org/10.1016/j.carbon.2020.11.067)

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Abstract

Diamond heat-spreaders for gallium nitride (GaN) devices currently depend upon a robust wafer bonding process. Bonding-free membrane methods demonstrate potential, however, chemical vapour deposition (CVD) of diamond directly onto a III-nitride (III–N) heterostructure membrane induces significant thermal stresses. In this work, these thermal stresses are investigated using an analytical approach, a numerical model and experimental validation. The thermal stresses are caused by the mismatch in the coefficient of thermal expansion (CTE) between the GaN/III-N stack, silicon (Si) and the diamond from room temperature to CVD growth temperatures. Simplified analytical wafer bow models underestimate the membrane bow for small sizes while numerical models replicate the stresses and bows with increased accuracy using temperature gradients. The largest tensile stress measured using Raman spectroscopy at room temperature was approximately 1.0 ±0.2GPa while surface profilometry shows membrane bows as large as 58μm. This large bow is caused by additional stresses from the Si frame in the initial heating phase which are held in place by the diamond and highlights challenges for any device fabrication using contact lithography. However, the bow can be reduced if the membrane is pre-stressed to become flat at CVD temperatures. In this way, a sufficient platform to grow diamond on GaN/III-N structures without wafer bonding can be realised.

  • Item type:Article
    ID code:74786
    Dates:
    Date
    Event
    28 November 2020
    Published
    28 November 2020
    Published Online
    22 November 2020
    Accepted
    Subjects:Science > Physics
    Department:Faculty of Science > Physics
    Depositing user: Pure Administrator
    Date deposited:03 Dec 2020 15:07
    Last modified:22 Apr 2024 18:40
    URI:https://strathprints.strath.ac.uk/id/eprint/74786
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