X X-X Y interface band mixing in GaAs/AlAs heterostructures

The in-plane dispersion of the X _{X, Y} states in a GaAs/AlAs “double-barrier structure” is measured by varying the angle of an in-plane magnetic field. When X _{X, Y} (1) states in the emitter AlAs layer tunnel into collector X_X,Y (m>1) states, a characteristic dumbbell shape is observed for the bias shift of the resonant tunneling peak versus magnetic field angle, with the major axis along [1 1 0] or [ 1̄ 1 0] . This corresponds to an elliptical constant energy surface in the collector AlAs layer which is rotated by 45° with respect to the bulk Fermi surface. We explain the new symmetry by X _X-X _Y interface band mixing which is closely analogous to the widely studied Γ-X _Z mixing. Our results provide new insight into the microscopic origin of both types of mixing.