Thermal Characterization and Modelling of AlGaN-GaN Multilayer Structures for HEMT Applications

Lisa Mitterhuber, René Hammer, Thomas Dengg and Jürgen Spitaler
Additional contact information
Lisa Mitterhuber: Materials Center Leoben Forschung GmbH, Roseggerstrasse 12, 8700 Leoben, Austria
René Hammer: Materials Center Leoben Forschung GmbH, Roseggerstrasse 12, 8700 Leoben, Austria
Thomas Dengg: Materials Center Leoben Forschung GmbH, Roseggerstrasse 12, 8700 Leoben, Austria
Jürgen Spitaler: Materials Center Leoben Forschung GmbH, Roseggerstrasse 12, 8700 Leoben, Austria

Energies, 2020, vol. 13, issue 9, 1-17

Abstract: To optimize the thermal design of AlGaN-GaN high-electron-mobility transistors (HEMTs), which incorporate high power densities, an accurate prediction of the underlying thermal transport mechanisms is crucial. Here, a HEMT-structure (Al 0.17 Ga 0.83 N, GaN, Al 0.32 Ga 0.68 N and AlN on a Si substrate) was investigated using a time-domain thermoreflectance (TDTR) setup. The different scattering contributions were investigated in the framework of phonon transport models (Callaway, Holland and Born-von-Karman). The thermal conductivities of all layers were found to decrease with a temperature between 300 K and 773 K, due to Umklapp scattering. The measurement showed that the AlN and GaN thermal conductivities were a magnitude higher than the thermal conductivity of Al 0.32 Ga 0.68 N and Al 0.17 Ga 0.83 N due to defect scattering. The layer thicknesses of the HEMT structure are in the length scale of the phonon mean free path, causing a reduction of their intrinsic thermal conductivity. The size-effect of the cross-plane thermal conductivity was investigated, which showed that the phonon transport model is a critical factor. At 300 K, we obtained a thermal conductivity of (130 ± 38) Wm −1 K −1 for the (167 ± 7) nm thick AlN, (220 ± 38) Wm −1 K −1 for the (1065 ± 7) nm thick GaN, (11.2 ± 0.7) Wm −1 K −1 for the (423 ± 5) nm thick Al 0.32 Ga 0.68 N, and (9.7 ± 0.6) Wm −1 K −1 for the (65 ± 5) nm thick Al 0.17 Ga 0.83 N. Respectively, these conductivity values were found to be 24%, 90%, 28% and 16% of the bulk values, using the Born-von-Karman model together with the Hua–Minnich suppression function approach. The thermal interface conductance as extracted from the TDTR measurements was compared to results given by the diffuse mismatch model and the phonon radiation limit, suggesting contributions from inelastic phonon-scattering processes at the interface. The knowledge of the individual thermal transport mechanisms is essential for understanding the thermal characteristics of the HEMT, and it is useful for improving the thermal management of HEMTs and their reliability.

Keywords: AlGaN-GaN HEMT; TDTR; thermal conductivity; thermal interface resistance; size effect; phonon transport mechanisms (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

Downloads: (external link)
https://www.mdpi.com/1996-1073/13/9/2363/pdf (application/pdf)
https://www.mdpi.com/1996-1073/13/9/2363/ (text/html)

Related works:
This item may be available elsewhere in EconPapers: Search for items with the same title.

Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text

Persistent link: https://EconPapers.repec.org/RePEc:gam:jeners:v:13:y:2020:i:9:p:2363-:d:355768

Access Statistics for this article

Energies is currently edited by Ms. Agatha Cao

More articles in Energies from MDPI
Bibliographic data for series maintained by MDPI Indexing Manager ().