Low-temperature equilibrium vertical transport through a two-dimensional electron gas

We have studied tunneling transport through a high-mobility two-dimensional electron gas in a GaSb/AlSb/ InAs/AlSb/GaSb heterostructure. In high perpendicular magnetic fields and at temperatures below 1 K the tunneling conductance shows deviations from regular Shubnikov-de Haas oscillations. An overall decrease in conductance with decreasing temperature is attributed to the formation of a Coulomb gap in the tunneling density of states. Reproducible conductance fluctuations are due to resonant tunneling possibly through interface-related states. © 1994.