Phonon thermal transport properties of GaN with symmetry-breaking and lattice deformation induced by the electric field

An Efficient Strategy for Searching High Lattice Thermal Conductivity Materials

“…To intuitively compare the relationship of phonon−phonon scattering phase space, the total P3 was calculated. The relationship order of total P3 for the three carbon allotropes is opposite to the relationship order of their SO, i.e., P3 (4-20) > P3 (12-18) > P3 (16)(17)(18)(19)(20)(21)(22), which indicates that higher SO or higher crystal symmetry results in a smaller phonon−phonon scattering phase space. WP3 has a similar relation and is shown in Figure 4b.…”

“…Thus, phonon anharmonicity also contributes to the crystal symmetry-dependent lattice thermal conductivity. By combining WP3 and Gruneisen parameters, the phonon−phonon scattering rate 1/τ (τ is the phonon lifetime) can be obtained, and the relationship order of 1/τ among the three allotropes (Figure 4c) is opposite to that of their SO, i.e., 1/τ (4-20) > 1/τ (12-18) > 1/τ (16)(17)(18)(19)(20)(21)(22), which verifies the above results that phonon−phonon scattering rate dominates the crystal symmetry-dependent lattice thermal conductivity.…”

“…Actually, basis and lattice also control the symmetry of the crystal structure (Figure ). Recently, several studies showed that crystal symmetry breaking could significantly enhance phonon–phonon scattering rates although the underlying reason is not well explored. − Accordingly, we hypothesize that crystal symmetry is another important parameter that may affect phonon–phonon scattering phase space in addition to n . Based on this hypothesis, we carefully selected 5 carbon allotropes from the Carbon Allotrope Database.…”

Variations of Interatomic Force Constants in the Topological Phonon Phase Transition of AlGaN

“…Both k-mesh sampling grids and kinetic energy cutoffs were examined with careful convergence tests. [7,10,11] Second interatomic FCs (2nd IFCs) were extracted based on the finite displacement supercell approach as implemented in open-source software Phonopy, [13] with a supercell size of 5 Â 5 Â 3 for wurtzite structure and corresponding 3 Â 3 Â 3 k-mesh grids. The Born effective charges and highfrequency dielectric constants were calculated by density functional perturbation theory for nonanalytical corrections of the dynamical matrix near the Gamma point in phonon dispersion calculations brought from polar effects.…”

“…In the GaN high-electron-mobility transistors (HEMTs), a very important GaN-based electronic, the near-junction thermal management, becomes critical, where heat spreading and phonon ballistic-diffusive thermal transport are coupled and contribute the most to the total thermal resistance. [4,5] In order to tackle the critical heat dissipation issues in GaNbased high-power electronics, first-principles calculations and thermal-physical experiments have been used to reveal the lattice thermal transport rules in single-crystal nitride semiconductors [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] as well as their alloy systems. [10,12,22] It has been recently reported that wurtzite III-nitride semiconductors contain topological phonons such as Weyl phonons and nodal ring phonons, [8,11,23,24] which are promising for realizing nondissipative or low-dissipative phonon thermal transport at surfaces and interfaces and improving the near-junction thermal management significantly due to the topologically protected surface phonon states.…”