Magnetotunnelling in semiconductor heterostructures
Fromhold, Timothy Mark (1990) Magnetotunnelling in semiconductor heterostructures. PhD thesis, University of Nottingham.
Experimental studies of magnetotunnelling in heterostructures have revealed series of resonances due to electrons tunnelling from a 2DEG in a lightly-doped emitter into magnetoquantised states in the collector contact of a single-barrier structure (Hickmott, 1987 and Snell et al. 1987) or in the quantum well of a double-barrier structure (Eaves et a1., 1988 and Leadbeater et a1., 1989). These experiments are very suitable for theoretical analysis since a transverse magnetic field (parallel to the barrier interfaces) has little effect on the electronic states of the 2DEG, provided the diamagnetic energy is much less than the binding energy of the bound state of the accumulation layer potential. The tunnelling electrons then have a small range of transverse momenta between +PF and -PF, where PF = l'lkF is the Fermi momentum in the 2DEG. This range determines the positions of the orbit centres of the magnetoquantised states into which the electrons are injected after emergence from the tunnel barrier. For the single-barrier heterostructures described in this thesis, these are interfacial Landau states corresponding to classical orbits in which the electron skips along the barrier interface. For double-barrier structures there are interfacial states at high magnetic fields and traversing states at low magnetic fields. Owing to the high electric field in the quantum well, the corresponding classical orbits are cycloidal trajectories which intersect both barrier interfaces (traversing states) or just one barrier interface (skipping states).
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