Quantum well field-effect transistor and method for manufacturing the same

A quantum well field-effect transistor (QWFET) includes a barrier layer, a quantum well layer, and a spacer layer. The quantum well layer is on the barrier layer. The barrier layer and the spacer layer comprise aluminum indium antimonide that is undoped. The quantum well layer comprises indium antimonide. The spacer layer is on the quantum well layer. The quantum well layer and the spacer layer are between a source contact and a drain contact. A gate contact is on a dielectric layer, which is on the spacer layer. By providing the barrier layer and the spacer layer as undoped layers, a performance of the QWFET may be improved.