Subthreshold mobility extraction for SOI MESFETs

The purpose of this paper is to extract the diffusion based mobility in SJT at low bias conditions to validate the drift-based results. To extract the diffusion coefficient for the SJT using our in-house 2D Monte Carlo device simulator, the following formulation is being used, D = = <(x(t) - )(v(t) - )> = 1/N /spl Sigma//sub i=1//sup N/ (x/sub i/(t) )(v/sub i/(t) - ) where /spl delta/x(t) and /spl delta/v(t) are the fluctuations of the particle position and velocity with respect to their ensemble averages. Using the above mentioned method we found that the simulated bulk diffusion coefficient is very close to the experimental values". Also, using the Einstein relation for non-degenerate semiconductors, we find that the corresponding low-field mobility values are on the order of 951 /spl sim/ 1121cm/sup 2//V-sec and confirm the drift based mobility calculation in the subthreshold region. Therefore, the mobility enhancement in SJT is being confirmed by two different but consistent methods, suggesting that this device structure exhibits higher cut-off frequency, which will make it suitable for application in r.f. micropower circuit design.