Submicron electron transport in silicon at 300 and 77 K

The transient and steady-state velocity-field characteristics of silicon samples of length 0.05, 0.1, 1, 5, and 20 μm are computed for fields of 5, 10, 20, 50, 100, and 200 kV/cm at 300 and 77 K. The computations are done assuming a parabolic band and including acoustic phonon scattering and intervalley phonon scattering with characteristic temperatures of 190 and 630 K. Effect of band nonparabolicity is also studied. The importance of collisions is discussed by comparing the computed curves with those obtained by excluding collisions. Electron transport is found to be collision-dominated down to 0.05 μm lengths at 300 K. At 77 K, collisions are not important for fields below 20 kV/cm for lengths of 0.05 and 0.1 μm but at higher fields collisions affect the characteristics significantly. Oscillations in average velocity caused by density modulation are observed at 77 K in 0.05 μm long sample for fields around 20 to 100 kV/cm.