Different dependence of band-to-band and Fowler-Nordheim tunneling on source doping concentration of an n-MOSFET

As the value of the maximum source doping concentration in the gate/source overlap area of an n-channel MOSFET (N/sub dmax/) varies, it has been observed that the edge Fowler-Nordheim (FN) tunneling through the gate oxide in the overlap area is changed significantly. In contrast, the N/sub dmax/ variation has little impact on band-to-band tunneling current (I/sub BB/) induced in the same overlap area. We attribute the independence of I/sub BB/ on N/sub dmax/ to the inhibition of band-to-band tunneling at the N/sub dmax/ location where silicon band bending becomes less than 1.1 eV resulting from increase of source doping concentration N/sub d/ beyond /spl sim/1.6/spl times/10/sup 19/ cm/sup -3/ (this value depends on the device used and its bias condition).