Transient Grating For Investigation Of Carrier Ambipolar Transport Kinetics In 6H-SiC

The carrier ambipolar diffusion coefficient, mobility and non-equilibrium carrier lifetime are crucial parameters for semiconductor materials. It is very important for the growth and application of semiconductor material, through measurement and analysis to the bipolar diffusion coefficient, migration rate and non-equilibrium carrier lifetime under different temperature and different excitation intensity. The research method in our experiment is light-induced transient grating. Light-induced transient grating is a all-optical, contactless experiment measures. Put the test sample in the interference area caused by two beams of coherent light, the transient grating is formed on the sample, the formed transient grating diffraction detecting light, through the diffraction signal of detecting light analysis of non-equilibrium carrier diffusion and recombination process and get the related parameters.Firstly, this paper analyzes the forming mechanism of the transient grating in semiconductor materials, get the relationship between grating attenuation rate and the kinemics process of non-equilibrium carrier diffusion and recombination. Set up a normal and a optical heterodyne transient grating experiment system respectively. Put the heterodyne detection technology to carrier relaxation dynamics process, improving the measure efficient and signal-to-noise ratio.Secondly, carry out the study in 6H-Si C use the two different transient grating experiment system that has set up, and measured the diffraction signal under several different grating period, get the free carrier grating attenuation rate under the different grating period, through the relationship between grating attenuation rate and grating period of transient grating get the carrier ambipolar diffusion coefficient, mobility and non-equilibrium carrier lifetime.Finally, explore the change of carrier bipolar diffusion coefficient, mobility and non-equilibrium carrier lifetime along with temperature and the intensity of excitation. We find from range 24℃to 200℃, excitation light intensity from range 1.6m W to 2.6m W, carrier bipolar diffusion coefficient is proportional to the excitation light intensity and Da~T-2.2, ?~T-3.4,non-equilibrium carrier lifetime decrease along with excitation light intensity and increase along with temperature.