LOW-TEMPERATURE EQUILIBRIUM VERTICAL TRANSPORT THROUGH A 2-DIMENSIONAL ELECTRON-GAS

We have studied tunneling transport through a high-mobility two-dimens ional electron gas in a GaSb/AlSb/InAs/AlSb/GaSb heterostructure. In h igh perpendicular magnetic fields and at temperatures below 1 K the tu nneling conductance shows deviations from regular Shubnikov-de Haas os cillations. An overall decrease in conductance with decreasing tempera ture is attributed to the formation of a Coulomb gap in the tunneling density of states. Reproducible conductance fluctuations are due to re sonant tunneling possibly through interface-related states.