  We have studied the tunneling properties of GaSb/AlSb/InAs/AlSb/GaSb
heterostructures, in which electrons and holes accumulate in the InAs and GaSb
regions respectively, under a magnetic field parallel to the interfaces. The
low-temperature (T = 4.2K), zero-bias magnetoconductance has shown a behavior
with field that evidences the two-dimensional character of both electrons and
holes and that has allowed us to determine the hole density and the
electron-hole separation. The observed field dependence of the current-voltage
characteristics is explained by the relative change in parallel momentum of
electrons and holes induced by the field.
