The peak‐to‐valley current ratio can be improved by adding a thin InAs layer in the well region of the GaSb/AlSb/GaSb/AlSb/InAs resonant interband tunneling structure. It is found that the ratio rises to more than 20 at room temperature for an InAs layer reaching 30 Å. Increasing the InAs layer beyond 30 Å the ratio gradually goes down. However, we also find as the added InAs layer is further increased to 240 Å, theI–Vcharacteristics change from single negative differential resistance (NDR) to multiple NDR behavior. Such interesting phenomena can be modeled theoretically due to the coupling effect of the electrons from the added InAs layer and the light holes from the GaSb layer in the well region.