Physics of Resonant Tunnelling

Abstract

A description is given of resonant tunnelling processes in double-barrier semiconductor heterostructures from the point of view of sequential theory. If a magnetic field is applied in the plane of the barrier interfaces, the energy and transverse momentum of the electrons injected into the quantum well through the emitter tunnel barrier can be varied independently by changing the applied voltage and magnetic field. This technique can be used to probe the energy and momentum spectrum of the subband states in a quantum well. In n-type wide-well structures, a detailed interpretation of niagneto-oscillations in the tunne1 current has been given in terms of semiclassical orbits of electrons in the well. In p-type structures with narrow wells, the dispersion curves of hole subbands, which are complicated by the strong mixing of light hole and heavy hole states, have been directly studied. Resonant tunnelling into the bound state of single donor atks in a quantum well has recently been observed. The magnetic field dependence of the tunnel current then gives a measure of the transverse momentum distribution and hence lateral extent of the donor wave function.

Magnetotunneling spectroscopy of a quantum well in the regime of classical chaos

“…4 T) that, except for 8 close to 90', only the lowest Landau level is occupied. Resonant tunneling occurs when the energy of this discrete emitter state coincides with the energy e"ofa subband in the QW [11]. As the bias voltage V is varied the tunneling electrons thus scan the energylevel spectrum of the QW.…”

“…For 8=90' both the emitter and QW states have plane-wave character in the transverse y, z directions. The tunneling matrix element only couples states with a velocity difference equal to that supplied by the Lorentz force as the electron traverses the mean distance between the 2DEG and nearside QW interface [11,12]. This requirement and that of energy conservation determine the allowed skipping states into which an electron can tunnel.…”