Resonant Γ-X-Γ tunneling in GaAs/AlAs/GaAs single barrier heterostructures at zero and elevated magnetic field

We report the observation of resonant tunneling and magneto-tunneling between states of different effective mass derived from zone centre (Γ) and zone edge (X) points of the Brillouin zone in single AlAs barrierdiodes. The nature of the X states involved (longitudinal X_z or transverse X_xy) is deduced from the observed resonances in the conductance versus bias characteristics at zero magnetic field (B). At finite B, theσ-V curves exhibit resonant magneto-tunneling with X_z Landau levels (LL), whilst no evidence of resonances with X_xy LLs is found. Clear observation of both LL index (in-plane momentum) conserving and non-conserving tunneling to X_z allows the transverse effective mass in AlAs to be determined. As a consequence of the different effective masses, momentum-conserving tunneling is inhibited at B = 0, but is restored when high B is applied.