Theory of Magnetotunnelling through Donors in the Quantum Well of Double-Barrier Resonant-Tunnelling Structures

The tunnel current from a two-dimensional electron gas (2DEG) into donor impurities in the quantum well of a double-barrier heterostructure is studied using the Bardeen Transfer-Hamiltonian formalism. Resonant tunnelling occurs when the donor level lies within the energy range of occupied 2DEG states. It is shown that in the presence of a magnetic field B normal to the current flow, the magnetocurrent J(B) is determined by the Fourier probability density of the donor wave function corresponding to the momentum p0 transferred to the tunnelling electrons by the Lorentz force. Then experimental J(B) curves, in principle, directly measure the donor wave function. The magnetocurrent is quenched when p0 greatly exceeds the width of the distribution of momentum Fourier components of the donor wave function.