The MBE growth and selected properties of InAs/AlSb n‐N isotype heterojunctions on n+‐GaAs substrates are described. Because of a large conduction‐band offset (1.35 eV), these junctions behave like Schottky barriers, with excellent rectification characteristics, despite the presence of a very high density (>107 cm−2) of threading dislocations resulting from the large lattice mismatch (7%) between AlSb and the GaAs substrate. The forward I‐V characteristics, corrected for series resistance, exhibit a large nonideality factor of about 1.8, suggesting that the main current flow is along a defect path, presumably related to the misfit dislocations. Reverse C‐V characteristics exhibit a perfectly linear 1/C2 vs V plot, from which a conduction‐band offset of 1.35±0.05 eV is deduced. This value is in excellent agreement with the value predicted from the known band offsets in InAs/GaSb and GaSb/AlSb.