Compressive Uniaxial Stress Bandstructure Engineering for Transferred-Hole Devices

The transport properties of holes in Si, Ge, and Si_1-xGe under high compressive stresses are studied with a Monte Carlo simulation method. Stress significantly improves the low-energy mass and mobility, while its effect is diminished in the high-energy bandstructure. The transient behavior of the carrier velocity exhibits a double-overshoot peak at high driving field. This double-overshoot behavior is manifested in carrier-velocity profiles in simulated short-channel PMOS devices. In steady state at lower field, the hole velocity exceeds the saturation velocity at high field. This leads to a negative differential resistance effect in simulated resistors. We propose to use this effect, generic to cubic semiconductors, for transferred-hole devices. An advantage of this approach is that it can be integrated into the conventional stress-engineered Si or Ge logic process.