Unipolar behavior of asymmetrically doped strained Si 0.5Ge 0.5 tunneling field-effect transistors

Abstract

We investigate here the impact of the dopant concentration in the source and drain regions on the ambipolar behavior of band-to-band tunneling field-effect transistors with compressively strained Si 0.5Ge 0.5 channels grown on Si on insulator. Source and drain areas were formed by BF 2 and As ion implantation to doses of 1 × 10 13, 1 × 10 14, and 1 × 10 15 cm -2. We show that the dopant concentration impacts the energy band alignment of source/drain and the channel region, and thus influences the tunneling current. The ambipolar device behavior is strongly reduced toward unipolar for source-to-drain implantation dose ratio of 100, but at the expense of the on-current, as compared to symmetric implanted devices. Moreover, our results indicate that for SiGe devices, the change of the B doping concentration has a greater impact on the tunneling currents than the variation of the As concentration. © 2012 American Institute of Physics.