Study On Thermal Transport Properties Of Gallium Arsenide At High Pressure And Silicon Carbide At Low Temperature

As an important indicator to evaluate the energy conversion efficiency and heat dissipation performance of semiconductor materials,thermal transport characteristics play an important role in the fields of space technology,energy technology,materials science,information technology and MEMS.Thermal transport properties are inherent properties of materials,but are also affected by the external environment,such as pressure and temperature.High pressure can change the elastic modulus,sound velocity,phonon density and interfacial bonding force of semiconductor materials,which is an important way to improve the performance of semiconductor materials.The low temperature strongly influences the phonon mean free path of the semiconductor material,and thus the scattering mechanism of its internal carriers.Therefore,it is of great significance to study the effects of high pressure and low temperature conditions on the thermal transport properties of semiconductor materials.In this paper,the dual-wavelength femtosecond laser time domain thermoreflectance method(TDTR)is combined with the diamond anvil cell(DAC)system and the low temperature system to achieve non-contact measurement of thermal properties of materials under high pressure and low temperature conditions.Through light heating,light measurement,and spectral pressure measurement,the sample is in a separate space with a pressure range of 0-500 GPa and a temperature range of 4-2000 K,which is not achievable by other methods of thermal transport characterization.The TDTR system is integrated with the high pressure system and the low temperature system by designing a high pressure sample stage and a DAC in-situ imaging system and processing a low temperature sample chamber mount.The TDTR optical path system and signal acquisition system are optimized by means of laser divergence angle changing,beam shaping,spot precise positioning and resonance filtering,which increases the system signal-to-noise ratio by three orders of magnitude.Based on the concept of relative sensitivity between free parameters and parameters to be tested,the sensitivity analysis of multi-parameter measurement was carried out,and the error analysis method of TDTR experimental measurement was established.The thermal conductivity of GaAs and the interfacial thermal conductance of Au/GaAs pressure dependence were obtained in the pressure range of 0-25 GPa.The GaAs phonon specific heat capacity,group velocity and relaxation time of the same pressure range were calculated by the first principle combined with the Boltzmann transport equation,and the thermal conductivity of GaAs was obtained.The theoretical calculations are consistent with the experimental measurement results.The thermal conductivity of 6H-SiC and the interfacial thermal conductance of Al/6H-SiC were obtained in the temperature range of 4-300 K.The thermal conductivity of 6H-SiC and 3C-SiC in the temperature range of 100-1000 K was calculated by the first principle combined with the Boltzmann transport equation.The thermal conductivity of Al/6H-SiC interface was calculated by DMM model.The theoretical calculations are consistent with the experimental measurements.