The current‐voltage (I‐V) behavior of a GaSb(p)/AlSb/InAs/AlSb/GaSb(p) resonant interband tunneling (RIT) heterostructure is analyzed experimentally and theoretically. The structure has been successfully grown on a (100)‐oriented GaAs substrate by molecular‐beam epitaxy, demonstrating that more exotic lattice‐matched substrates (such as InAs or GaSb) are not required for RIT devices. Theoretical simulations ofI‐Vbehavior are developed, employing a two‐band tight‐binding model. ExperimentalI‐Vcurves show pronounced negative differential resistance, with a peak‐to‐valley current ratio of 8.3 at 300 K. Good agreement is observed between measured and calculated peak current densities, consistent with light‐hole tunneling through the confined InAs conduction‐band state.