| 1. |
- Slomski, Michael, et al.
(författare)
-
Thermal conductivity of bulk GaN grown by HVPE: Effect of Si doping
- 2017
-
Ingår i: Physica status solidi. B, Basic research. - : WILEY-V C H VERLAG GMBH. - 0370-1972 .- 1521-3951. ; 254:8
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity of bulk GaN grown by Hydride Phase Vapor Epitaxy with intentional Si doping was measured using the 3 method. The effect of Si concentration ranging from 1.6x10(16) to 7x10(18)cm(-3) on the thermal conductivity was studied over the temperature range of 295-470K. The room temperature thermal conductivity was found to decrease with increasing Si doping from 245 to 210W/m.K. Also, for each Si doped sample the thermal conductivity decreases with increasing temperature. The experimental data were analysed by a modified Callaway model and the contribution of different resistive phonon scattering process was examined. It was found that in n-type GaN the phonon-free-electron scattering became an important resistive process that leads to a reduction of the thermal conductivity at high temperatures. At the highest free electron concentrations, electronic thermal conduction was found to play a role in addition to lattice thermal conduction and compete with the effects of phonon-free-electron scattering. (C) 2017 WILEY-VCH Verlag GmbH amp; Co. KGaA, Weinheim
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Tran, Dat, et al.
(författare)
-
On the thermal conductivity anisotropy in wurtzite GaN
- 2023
-
Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 13:9
-
Tidskriftsartikel (refereegranskat)abstract
- GaN-based power devices operating at high currents and high voltages are critically affected by the dissipation of Joule heat generated in the active regions. Consequently, knowledge of GaN thermal conductivity is crucial for effective thermal management, needed to ensure optimal device performance and reliability. Here, we present a study on the thermal conductivity of bulk GaN in crystallographic directions parallel and perpendicular to the c-axis. Thermal conductivity measurements are performed using the transient thermoreflectance technique. The experimental results are compared with a theoretical calculation based on a solution of the Boltzmann transport equation within the relaxation time approximation and taking into account the exact phonon dispersion. All factors that determine the thermal conductivity anisotropy are analyzed, and the experimentally observed small anisotropy factor is explained.
|
|
| 5. |
- Tran, Dat, et al.
(författare)
-
Phonon-boundary scattering and thermal transport in AlxGa1-xN: Effect of layer thickness
- 2020
-
Ingår i: Applied Physics Letters. - : AMER INST PHYSICS. - 0003-6951 .- 1077-3118. ; 117:25
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal conductivity of AlxGa1-xN layers with 0 <= x <= 0.96 and variable thicknesses is systematically studied by combined thermoreflectance measurements and a modified Callaway model. We find a reduction in the thermal conductivity of AlxGa1-xN by more than one order of magnitude compared to that of GaN, which indicates a strong effect of phonon-alloy scattering. It is shown that the short-mean free path phonons are strongly scattered, which leads to a major contribution of the long-mean free path phonons to the thermal conductivity. In thin layers, the long-mean free path phonons become efficiently scattered by the boundaries, resulting in a further decrease in the thermal conductivity. Also, an asymmetry of thermal conductivity as a function of Al content is experimentally observed and attributed to the mass difference between Ga and Al host atoms.
|
|
| 6. |
- Tran, Dat, et al.
(författare)
-
Thermal conductivity of ultra-wide bandgap thin layers - High Al-content AlGaN and beta-Ga2O3
- 2020
-
Ingår i: Physica. B, Condensed matter. - : ELSEVIER. - 0921-4526 .- 1873-2135. ; 579
-
Tidskriftsartikel (refereegranskat)abstract
- Transient thermoreflectance (TTR) technique is employed to study the thermal conductivity of beta-Ga2O3 and high Al-content AlxGa1-xN semiconductors, which are very promising materials for high-power device applications. The experimental data are analyzed with the Callaways model taking into account all relevant phonon scattering processes. Our results show that out-of-plane thermal conductivity of high Al-content AlxGa1-xN and (-201) beta-Ga2O3 is of the same order of magnitude and approximately one order lower than that of GaN or AlN. The low thermal conductivity is attributed to the dominant phonon-alloy scattering in AlxGa1-xN and to the strong Umklapp phonon-phonon scattering in beta-Ga2O3. It is also found that the phonon-boundary scattering is essential in thin beta-Ga2O3 and AlxGa1-xN layers even at high temperatures and the thermal conductivity strongly deviates from the common 1/T temperature dependence.
|
|
