First-Principles Modeling of Quantum Effects From Defects in 4H-SiC MOSFETs

Defect plays an important role in carrier transports of electronic devices. But its quantization in transport simulations is still a challenging task. Here, we propose a full quantum transport simulation approach and demonstrate its application to defective 4H-SiC MOSFET channels. The simulation starts from the tight-binding (TB) model construction of a perfect 4H-SiC crystal chain representing the local slice of a MOSFET channel, which is carried out by the density-functional theory (DFT) and Wannier transformation. Then, the periodicity of this chain is broken by importing the defect trap levels into the model, with TB parameters from defective 4H-SiC supercells and charge transition level (CTL) calculations. To enhance the reliability, the carrier scattering rates by first principles electron-phonon coupling (EPC) calculations are also included in the model. Using this approach, transport properties of 4H-SiC channels each containing a single trap level are simulated, including the threshold voltage, subthreshold swing (SS), field effect mobility, and on -state current. The trap levels are either induced by C vacancies (${V}_{C}$) and interstitials (${C}_{i}$) or from other relevant works. The results reveal that the trap levels near the conduction band minimum will degrade the electron transport more severely. Specifically, the degradation by${V}_{C}$is more pronounced than that by${C}_{i}$. Moreover, the detection of quantum coupling effects between closely spaced defects leads to more severe device performance degradations, demonstrating that the proposed simulation approach can effectively capture the quantum effects of defects in 4H-SiC MOSFET channels.