Infrared Spectroscopy of Lower Dimensional Electron Systems

In semiconductor devices that are the backbone of modern technology the conducting electrons are often confined by field effect or doping near an interface potential barrier and form a quasi-two-dimensional electron system. High resolution lithography and refined etching techniques now make it possible to laterally confine such originally two-dimensional electron systems to narrow channels with widths comparable to the de-Broglie wavelengths of the electrons. The transition from two-dimensional to one-dimensional electronic behavior that occurs as lateral confinement lengths are lowered to about 100 nm is directly observed with infrared spectroscopy of the electronic excitations in laterally microstructured metal-oxide-semiconductor and semiconductor-heterojunctions devices.