Resonant Γ-Χ-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 (Gamma) and zone edge (X) points of the Brillouin zone in single AlAs barrier diodes. 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, the sigma-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. (C) 1998 Academic Press Limited.