I-MOS: a novel semiconductor device with a subthreshold slope lower than kT/q

One of the "fundamental" problems in the continued scaling of MOSFETs is the 60 mV/decade room temperature limit in subthreshold slope. In this paper, we report initial studies on a new kind of transistor, the I-MOS. The I-MOS uses modulation of the breakdown voltage of a gated p-i-n structure in order to switch from the OFF to the ON state and vice versa. Since impact-ionization is an abrupt function of the electric field (or the carrier energy), simulations show that the device has a subthreshold slope much lower than kT/q. Simulations also show that it is indeed possible to make complementary circuits with switching speeds comparable to or exceeding CMOS. Experimental results on a silicon based prototype verify the basic concept and show very steep subthreshold slopes with high speed turn-on and turn-off. Lower bandgap materials are also being investigated to reduce the value of the breakdown voltage and permit lower voltage operation.