We propose and study a new GaSb/InAs/GaSb/AlSb/InAs broken‐gap interband tunneling diode by varying the thicknesses of the InAs layer. A twice‐higher peak current density and a three‐times‐higher peak‐to‐valley current ratio in the proposed structure with a 30‐A˚‐thick InAs layer were observed relative to the structure with no InAs layer. This result indicates that the characteristic of the negative differential resistance can be improved simply by placing a thin effective InAs barrier on the GaSb side of the GaSb/AlSb/InAs single‐barrier structure. The increase of the peak current is interpreted as the result of forming a quasi‐bound state in the GaSb well. This interpretation is supported by the observation that the current‐voltage characteristic of the proposed structure is similar to that of a conventional GaSb/AlSb/GaSb/AlSb/InAs double‐barrier interband tunneling structure.