Published in IET Science, Measurement and Technology Received on 28th October 2010 Revised on 22nd December 2011 doi: 10.1049/iet-smt.2011.0031 ISSN 1751-8822 Locally one-dimensional finite-difference time-domain scheme for the full-wave semiconductor device analysis R. Mirzavand 1 A. Abdipour 1 W.H.A. Schilders 2 G. Moradi 1 M. Movahhedi 3 1 Microwave/mm-wave and Wireless Communication Research Lab, Radio Communications Center of Excellence, Electrical Engineering Department, Amirkabir University of Technology, Tehran, Iran 2 Department of Mathematics and Computer Science, Eindhoven University of Technology, Eindhoven, The Netherlands 3 Electrical Engineering Department, Shahid Bahonar University of Kerman, Kerman, Iran E-mail: adbipour@aut.ac.ir Abstract: The application of an unconditionally stable locally one-dimensional finite-difference time-domain (LOD-FDTD) method for the full-wave simulation of semiconductor devices is described. The model consists of the electron equations for semiconductor devices in conjunction with Maxwell’s equations for electromagnetic effects. Therefore the behaviour of an active device at high frequencies is described by considering the distributed effects, propagation delays, electron transmit time, parasitic elements and discontinuity effects. The LOD-FDTD method allows a larger Courant–Friedrich– Lewy number (CFLN) as long as the dispersion error remains in the acceptable range. Hence, it can lead to a significant time reduction in the very time consuming full-wave simulation. Numerical results show the efficiency of the presented approach. 1 Introduction Global modelling of mm-wave circuits is an accurate method which considers the distributed effects, parasitic elements and discontinuities. The main issue of this modelling is the full-wave analysis of their active devices (ADs). The equations that describe the transport physics in conjunction with Maxwell’s equations must be solved in an accurate analysis to predict the interactions between the carriers and the propagating wave inside the devices [1, 2]. A number of different approaches for the simulation of semiconductor devices have been developed in the past. Most of these techniques are fundamentally dependent upon the solution of the Poisson equation along with the basic carrier transport equations. In this paper, the semiconductor analysis is based on the time-domain drift- diffusion model (DDM) [3]. The set of DDM equations contains the Poisson equation and the carrier transport equations, obtained by splitting the Boltzmann transport equation (BTE) into its first two moments. The DDM model assumes that the carrier temperature is equal to the semiconductor lattice temperature. Therefore the carrier velocity is only dependent on the electric field. In comparison with the other more rigorous techniques, the DDM is a relatively simple one with better convergence of the algorithm and shorter computational time for the numerical modelling of semiconductor devices. Thus, it is more suitable for a design engineer to use for first steps. Another more accurate model can be used to improve the final structure. Even for simple semiconductor equations, the common FDTD simultaneous simulation of those and Maxwell’s equations is very time consuming because of the Courant– Friedrich–Lewy (CFL) stability condition on the simulation time-step size [1, 2]. Recently, a new implicit method, called the locally one-dimensional finite-difference time-domain (LOD-FDTD) method, has been introduced to solve Maxwell’s equations [4–7]. This method is an attractive alternative to the standard FDTD because of its unconditional stability with moderate computational overhead. The ADI- FDTD and LOD-FDTD methods can particularly useful for problems involving devices with fine geometric features that are much smaller than the wavelengths of interest [8], as they are free of CFL limit. However, LOD-FDTD presents a better computational efficiency than the ADI-FDTD [9]. This paper presents a semi-implicit numerical method to solve the DDM equation based on the LOD-FDTD scheme. Then, using the LOD-FDTD method for the electromagnetic (EM) equations as well, an unconditionally stable method for the full-wave simulation of semiconductor devices is presented to remove the CFL limit of time-step size. The simulation results show the efficiency of LOD-FDTD method with respect to the conventional FDTD and ADI-FDTD methods. 78 IET Sci. Meas. Technol., 2012, Vol. 6, Iss. 2, pp. 78–84 & The Institution of Engineering and Technology 2012 doi: 10.1049/iet-smt.2011.0031 www.ietdl.org