Quantum capacitance devices.

Two dimensional electron gas (2DEG) in a quantum well or an inversion layer, unlike an ordinary grounded metallic plane, does not completely screen an applied transverse electric field. Owing to its Fermi degeneracy energy, a 2DEG manifests itself as a capacitor in series, whose capacitance per unit area equals C sub Q = me sup 2 /pi h sup 2, where m is the effective electron mass in the direction transverse to the quantum well. Partial penetration of an external field through a highly conducting 2DEG allows the implementation of several novel high-speed devices, including a 3-terminal resonant-tunneling transistor and a gate-controlled thermionic emission transistor.