Magnetotunneling in a two-dimensional electron-hole system near equilibrium

We have measured the zero-bias differential tunneling conductance of InAs/AlSb/GaSb/AlSb/InAs heterostructures at low temperatures (1.7 K<T<60 K) and under a magnetic field at various angles with the heterostructure's interfaces. Shubnikov-de Haas oscillations in the magnetoconductance reveal the two-dimensional (2D) character of the electrons accumulated at the InAs interfaces and yield their number in each of them. The temperature dependence of the oscillations suggests the formation of a field-induced energy gap at the Fermi level, similar to that observed before in simpler 2D-2D tunneling systems. A calculation of the magnetoconductance that considers different 2D densities in the two InAs electrodes agrees with the main observations, but fails to explain features that might be related to the presence of 2D holes in the GaSb region.