LATERAL RESONANT TUNNELING TRANSISTORS EMPLOYING FIELD-INDUCED QUANTUM-WELLS AND BARRIERS

Future scaled transistors may well have dimensions significantly less than 100 nm and be operated at temperatures low enough for quantum effects to be appreciable. Such effects, while undesirable for conventional transistors, may be put to good use in future devices. We describe here some preliminary experimental results of quantum-effect modulation-doped field-effect transistors (MODFET's) with a variety of nanometer gate geometries. The gate geometries were such that various quantum wells and barriers were formed in the channel of the MODFET's through the field effect imposed by the novel gate structures, and that the transport of the electrons was affected by resonant tunneling. The devices were fabricated using a combination of molecular beam epitaxy and electron beam lithography. Electrical measurements of the devices at 4.2 K showed resonant tunneling effects and, in particular, showed that resonant tunneling is more pronounced for a system of quantum wells confined in three dimensions than in two. For these quantum effects to be appreciable at practical temperatures, say 77 K, the feature size of the gate geometries should be smaller than 50 nm.