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 microe lectronic circuits. These quantum devices can be made in the Si/SiGe system , which is compatible with Si technology. We have fabricated Si/SiGe RTDs w ith submicron lateral dimensions and have studied their electrical properti es. In particular, we have measured the size-dependence of these properties in p-type mesa-etched dots sind wires. We find that the I-V characteristic s can be strongly influenced by strain relaxation at the side walls of the heterostructure. Here we study this effect of strain relaxation on the quan tum-well subbands, The lateral dimensions of the devices ranged from 10 mu m down to 230 nm. It was found that both the subband-edge energy and the ki netic energy associated with the in-plane motion of holes are strongly infl uenced by the size and shape of the device. This result is explained by ana lyzing the effect of strain relaxation on the valence band for the two geom etries.