GIANT CAPACITANCE OSCILLATIONS RELATED TO THE QUANTUM CAPACITANCE IN GAAS ALAS SUPERLATTICES

We have observed periodic current and capacitance oscillations with in creasing bias on doped GaAs/AlAs superlattices at a temperature of 77 K. The maximum of the observed capacitance is larger than usual geomet ric capacitances in superlattices, being comparable to the quantum cap acitance of the two-dimensional (2D) electron system proposed by Luryi . A model based on well-to-well sequential resonant tunneling due to t he movement of the boundary between the electric field domains in supe rlattice was proposed to explain the origin of the giant capacitance o scillations. It was demonstrated that the capacitance at the peaks of capacitance-voltage (C-V) characteristics reflects the quantum capacit ance of the space-charge region at the boundary between the domains (a novel 2D electron system).