Numerical Simulations of Semiconductor Devices by Streamline-Diffusion Methods

Theoretical and practical aspects of the design and implementation of the streamline-diffusion (SD) method for semiconductor device models are explored systematically. Emphasis is placed on the hydrodynamic (HD) model, which is computationally more challenging than the drift-diffusion (DD) model, but provides some important physical information missing in the DD model. We devise a non-symmetric SD method for device simulations. This numerical method is uniformly used for the HD model (including a proposed simplification (SHD)) and the DD model. An appropriate SD operator is derived for the general non-symmetric convection-diffusion system. Linear stability analysis shows that our proposed numerical method is stable if the system can be symmetrized. Stability arguments and numerical experiments also suggest that the combination of the method of lines and the semi-discrete SD method may not be appropriate for the transient problem, a fact which often has been ignored in the literature. An efficient method, consistent with the SD method used for conservation laws, is developed for the potential equation. The method produces a more accurate electric field than the conventional Galerkin method. Moreover, it solves for the potential and electric field in a decoupled manner. We apply our numerical method to the diode and MESFET devices. Shocks for the diode in one and two space dimensions and the electron depletion near the gate for the MESFET in two space dimensions are simulated. Model comparisons are implemented. We observe that the difference in solutions between the HD and DD models is significant. The solution discrepancy between the full HD and SHD models is almost negligible in MESFET simulation, as in many other engineering applications. However, an exceptional case is found in our experiments.