He. Nilsson et al., INVESTIGATION OF HOT-CARRIER TRANSPORT IN SILICON PERMEABLE BASE TRANSISTORS, I.E.E.E. transactions on electron devices, 43(6), 1996, pp. 924-931
The effects of variations in the source to drain distance have been in
vestigated for several highly doped Permeable Base Transistor (PET) st
ructures. A detailed study of the hot electron transport in these stru
ctures is presented using a 2-D self-consistent full hand Monte Carlo
(MC) simulation program, The PET structures considered are the overgro
wn, etched source and etched Brain PET, Finally we have simulated a st
ructure where both the source and the drain have been etched, All stru
ctures have a high doping level in the channel (10(17) cm(-3)) and are
operating under a gate biasing far from the threshold voltage, The et
ched structure shows a larger increase in the unity current gain frequ
ency (f(I)) than the overgrown structure as the source to drain distan
ce decreases, By optimizing the source to drain distance of the etched
source PBT, the f(T) can be increased by a factor of two, Our Monte C
arlo result has been compared with an ordinary drift-diffusion (DD) mo
del and a more advanced energy transport (ET) model, The difference be
tween the MC anti DD model is largest for the etched structures, while
it is less significant for the overgrown, structure. However, all str
uctures considered in this work, long and short channel devices, show
a larger dc current level in the MC model, This is related to the larg
e electric field and high carrier temperature near the gate depletion
region.