The Influence of Strain Relaxation on the Electrical Properties of Submicron Si/SiGe Resonant-Tunneling Diodes

Resonant tunneling devices (RTDs) and resonant tunneling transistors (RTTs) are possible building blocks with increased functionality of future microelectronic circuits. These quantum devices can be made in the Si/SiGe system, which is compatible with Si technology. We have fabricated Si/SiGe RTDs with submicron lateral dimensions and have studied their electrical properties. In particular, we have measured the size-dependence of these properties in p-type mesa-etched dots and wires. We find that the I-V characteristics can be strongly influenced by strain relaxation at the side walls of the heterostructure. Here we study this effect of strain relaxation on the quantum-well subbands. The lateral dimensions of the devices ranged from 10 m down to 230 nm. It was found that both the subband-edge energy and the kinetic energy associated with the in-plane motion of holes are strongly influenced by the size and shape of the device. This result is explained by analyzing the effect of strain relaxation on the valence band for the two geometries.