Phonon-boundary scattering and thermal transport in AlxGa1−xN: Effect of layer thickness

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.

The role of pressure on lattice thermal conductivity and its related thermodynamical parameters in In0.53Ga0.47As nanofilms

“…The term for alloy scattering defined at which phonons scatter with the alloy is comparable to the rate of phonon-isotope scattering. The parameter ( A ) signifies the alloy parameter, which quantifies the intensity of the alloy's scattering effect, 42 and is calculated by , representing the strength of the mass difference interaction, which for In 0.53 Ga 0.47 As, is calculated as follows: 43 …”

Thermal conductivity of wide and ultra-wide bandgap semiconductors

“…(1.47) with the solution of the Boltzmann transport equation for thin layers [41] and used to model the thickness dependence of the thermal conductivity of GaN [41,48]. In the analysis of the experimental data included in this thesis, we use a = 1.5, the value extracted from the experimental thickness dependence of the thermal conductivity of Al x Ga 1−x N with various compositions [49].…”

Super-Suppression of Long-Wavelength Phonons in Constricted Nanoporous Geometries

“…Even traditionally inefficient thermoelectric materials like Si can become highly efficient when they are nanostructured [3,4] or when nanopores are introduced into the lattice [5]. The size of the nanostructured features and the distance between them determines the scattering specifics, typically scattering phonons of similar mean free paths (MFPs) more effectively [6][7][8][9]. For example, short MFPs are effectively scattered by point defects or alloying; medium MFPs by nanopores, nanoprecipitates or superlattices; and long MFPs by large-scale grain boundaries in polycrystalline materials.…”