Monte Carlo simulations of submicron SOI-LBJTs

The motivation for research into silicon-on-insulator lateral bipolar junction transistors (SOI-LBJT) is to take advantage of both the high current-drive capability of high-speed bipolar transistors and the mass production of advanced CMOS technology. Optimum transistor design is ultimately based on a full understanding and accurate modelling of the charge-carrier transport in the device. Monte Carlo simulation has been used to provide a microscopic description of the steady state and transient charge transport in a novel SOI-LBJT. The simulated device is similar to that investigated experimentally by Gomez et al. (Microelectron. Journal vol. 31, pp.199-205, 2000). The simulation provides information on the microscopic details of carrier behavior, including carrier velocity, kinetic energy and carrier density, as a function of position in the device. Four devices are described here and the effects of junction depth and silicon layer thickness are investigated. Monte Carlo simulations were also carried out to study the high frequency performance of the devices. Detailed time-dependent voltage signal analysis was carried out to test the device response and derive the frequency bandwidth. A sine voltage pulse is applied to the base and the resulting collector and base currents used to calculate the current gain as a function of frequency. The common-emitter current gain of device 2 could have a cut off frequency f/sup i//sub T/ approaching 35/spl plusmn/5 GHz if the shallow emitter and collector contact resistances are minimized.