A modified drift-diffusion model for sub-micron devices

It is well recognized that the use of low field mobility /spl mu/ and the diffusion constant D in the drift-diffusion equation becomes questionable in narrow based HBTs or short gate FETs. For short samples the transport parameters not only become field and position dependent, but also initial distribution dependent. Moreover, the diffusion constant, which is defined for a stationary process, becomes an ill-defined parameter in very short devices. In this paper a modified drift-diffusion model that can be used in sub-micron devices is reported.