Monte Carlo simulation of transport in technologically significant semiconductors of the diamond and zinc-blende structures. II. Submicrometer MOSFET's

For pt.I see ibid., vol.38, no.3, p.634-49, March 1991. MOSFETs with channel lengths smaller than 0.25 mu m with substrates of four different semiconductors and one alloy of the diamond and zinc-blende structures (n-channel Ge, Si, GaAs, InP, In/sub 0.53/Ga/sub 0.47/As, and p-channel Si) were simulated at 77 and 300 K with a self-consistent two-dimensional Monte Carlo program. With the exception of the In-based materials, the speed of the devices appears to be largely independent of the semiconductor. This universal behavior results from the similarity among the medium-energy-scale features of the band structures of the cubic semiconductors. Low-energy concepts, such as mobility and effective mass, fail to describe charge transport as carriers populate a larger fraction of the Brillouin zone in these small devices driven at reasonably high biases. The assumptions made, the approximations used, and, in particular, the meaning of the words speed and reasonably mentioned above are discussed.>