MONTE-CARLO SIMULATION OF TRANSPORT IN TECHNOLOGICALLY SIGNIFICANT SEMICONDUCTORS OF THE DIAMOND AND ZINCBLENDE STRUCTURES .2. SUBMICROMETER MOSFETS

MOSFET's with channel length 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, In0.53 Ga0.47 As, and p-channel Si) have been 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. We discuss the assumptions made, the approximations employed, and, in particular, the meaning of the words "speed" and "reasonably" mentioned above.