Study On The Characteristies And Radiation Response Of SiC Material And Devices

The attractive characteristics and the excellent electric properties of SiC has led us to the fabrication of electronic devices used in strong radiation environments. For the application of SiC devices to radiation fields, it is important to know the irradiation effects and characteristics of SiC materials and devices. The main contributions in this thesis are as following:Temperature- and electric field-dependent electron transport in 6H-S1C is studied by single-particle Monte Carlo technique. The physical model used in the simulation is developed considering the main scattering mechanisms in details. The results show the excellent high-temperature properties and anisotropy of mobility. The ratio Auç› ./p~ in 6H-SiC is about 5. The simulated results are in good agreement with measured data in a wide range of temperature and electric field.The influence of incomplete ionization of impurity in 6H-SiC on MOSFET electrical characteristics is investigated considering the Frenkel-Pool effect, Which can enhance the impurity ionization by lowing the effective barrier height. And a new numerical Charge-Sheet model for SiC MOS inversion layers is presented based on an numerical solution of a one-dimension Poisson equation. The results obtained from this approach are in good agreement with the measured values. The study shows that the impact of incomplete ionization on SiC MOSFET is more notable in subthreshold region than in strong inversion region.The total number of defects induced by electron irradiation in 4H-SiC is calculated theoretically. The deep level defect of EH6/EH7 is considered to play the most important role in carrier recombination from the comparison of all kinds of possible electron traps. A model of the minority carrier lifetime damage constant is presented. The model is proved to be reasonable by good match with experimental data.In respect of SiC devices, an analytical model of 6H-SiC JFET to well match the experimental results is proposed. The radiation response of SiC JFET in room temperature to 300 C is simulated with the analysis for the neutron irradiation effect such as carrier removal, mobility degradation and space charge density decrease. The degradation of the electrical characteristics in SiC pn junctions irradiated by neutron is attributed to the recombination centers and the electric field effect on the thermal emission of traps within the depletion region. The relationship of the ideality factor to the applied voltage is theoretically studied. A model of the SiC pn junctions irradiated by neutron is presented.The effects of radiation induced oxide trapped charge and SiC/Si02 interface state density on inversion layer mobility is studied systematically. Firstly, a new interface roughness scattering model is developed using exponential autocovariance functions. The simulation results show that the electron mobility calculated using the exponential model are in good agreement with the experiment data. Then, a comprehensive an~tlyticai model for coulomb scattering in 6H-SiC inversion layers is presented considering all the coulomb effects of the charged-centers near the SiCISiO2 interface. This model takes into account the effects of the charged-centers correlation. Finally, the electron mobility in 6H-SiC inversion layers is studied by single-particle Monte Carlo technique. The simulation results fit the experimental data very well. The study shows that coulomb scattering becomes more important at low transverse-electric field and both the density and the distribution of charged-centers play an important role in electron transport in SiC inversion layers.The radiation response and electric characteristics of 6H-SiC MOS structure is studied with experiment for the first time. It is found that the main electronic conduction mechanism in the high field regions of the I-V characteristics is identified to be FowlerNordheim tunneling. The effect of y ray on SiC MOS C-V characteristics depends strongly on the bias voltage applied to the gate elec...