Thermal Transport Properties Study On InGaN And AlGaN Luminescent Materials

InGaN and AlGaN are the key materials in GaN-based LED devices.However,the research on the thermal transport properties of InGaN and AlGaN is still relatively few,and most of them focus on the measurement of thermal conductivity and the design of LED devices,lacking systematic exploration on the mechanism of thermal conductivity change of materials.In this paper,the first-principles calculation method combined with the phonon Boltzmann transport equation is used to study the thermal transport of GaN,InGaN and AlGaN from the aspects of crystal structure,phonon contribution of thermal conductivity,phonon transport properties and electronic properties,etc.The research results in this paper reveal the mechanism of thermal conductivity change of GaN alloy materials and provide theoretical basis for heat dissipation design of optoelectronic devices.The main results are as follows:The thermal conductivities of InGaN and AlGaN are calculated,in which the thermal conductivities of InGaN along the in-plane and out-of-plane directions are 7.38 and 8.62W/m K respectively,while those of AlGaN along the in-plane and out-of-plane are 12.45 and 11.80 W/m K respectively,which are greatly reduced compared with those of GaN.Further analysis of the phonon and electronic properties of the materials shows that the reasons for the decrease of thermal conductivity of InGaN and AlGaN relative to GaN are as follows: 1.The phonon group velocity and phonon relaxation time of InGaN and AlGaN are lower than those of GaN,and the thermal conductivity is proportional to the phonon group velocity,and the phonon lifetime becomes shorter with the decrease of phonon relaxation time,which leads to the lower thermal conductivity of materials;2.The phonon anharmonicity of InGaN and AlGaN is stronger than that of GaN,and the increase of phonon anharmonicity will have a favorable influence on the phonon-phonon scattering of materials,thus making the thermal conductivity of InGaN and AlGaN lower;3.Influenced by the atomic radius and mass of In atoms and Al atoms,the crystal symmetry is destroyed,and the polarity of In-N bonds and Al-N bonds is stronger than that of GaN,which has a negative impact on the thermal conductivity of InGaN and AlGaN.In addition,it is found that the anisotropy of thermal conductivity of AlGaN is opposite to that of GaN,because the contribution of phonons in AlGaN in the in-plane and out-of-plane directions has a different rate of change than that of GaN,and the amplitude of change in in-plane is much larger than that in out-of-plane.Based on the research in this paper,the mechanism of thermal transport properties of GaN,InGaN and AlGaN is revealed intuitively and deeply,which has guiding significance for the wide application of GaN and related materials,the thermal management of LED devices and the research of thermal transport properties of related semiconductor materials.