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Title: Size effects in the thermal conductivity of gallium oxide (β-Ga{sub 2}O{sub 3}) films grown via open-atmosphere annealing of gallium nitride

Gallium nitride (GaN) is a widely used semiconductor for high frequency and high power devices due to of its unique electrical properties: a wide band gap, high breakdown field, and high electron mobility. However, thermal management has become a limiting factor regarding efficiency, lifetime, and advancement of GaN devices and GaN-based applications. In this work, we study the thermal conductivity of beta-phase gallium oxide (β-Ga{sub 2}O{sub 3}) thin films, a component of typical gate oxides used in such devices. We use time domain thermoreflectance to measure the thermal conductivity of a variety of polycrystalline β-Ga{sub 2}O{sub 3} films of different thicknesses grown via open atmosphere annealing of the surfaces of GaN films on sapphire substrates. We show that the measured effective thermal conductivity of these β-Ga{sub 2}O{sub 3} films can span 1.5 orders of magnitude, increasing with an increased film thickness, which is indicative of the relatively large intrinsic thermal conductivity of the β-Ga{sub 2}O{sub 3} grown via this technique (8.8 ± 3.4 W m{sup −1} K{sup −1}) and large mean free paths compared to typical gate dielectrics commonly used in GaN device contacts. By conducting time domain thermoreflectance (TDTR) measurements with different metal transducers (Al, Au, and Au with a Ti wettingmore » layer), we attribute this variation in effective thermal conductivity to a combination of size effects in the β-Ga{sub 2}O{sub 3} film resulting from phonon scattering at the β-Ga{sub 2}O{sub 3}/GaN interface and thermal transport across the β-Ga{sub 2}O{sub 3}/GaN interface. The measured thermal properties of open atmosphere-grown β-Ga{sub 2}O{sub 3} and its interface with GaN set the stage for thermal engineering of gate contacts in high frequency GaN-based devices.« less
Authors:
; ; ;  [1] ; ;  [2] ;  [3]
  1. Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States)
  2. Department of Physics and Astronomy, James Madison University, Harrisonburg, Virginia 22807 (United States)
  3. Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States)
Publication Date:
OSTI Identifier:
22413169
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 8; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANNEALING; COMPARATIVE EVALUATIONS; DIELECTRIC MATERIALS; ELECTRICAL PROPERTIES; ELECTRON MOBILITY; GALLIUM NITRIDES; GALLIUM OXIDES; INTERFACES; LAYERS; LIFETIME; MEAN FREE PATH; PHONONS; POLYCRYSTALS; SAPPHIRE; SEMICONDUCTOR MATERIALS; THERMAL CONDUCTIVITY; THIN FILMS; TRANSDUCERS