Unipolar behavior of asymmetrically doped strained Si0.5Ge0.5 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 Si0.5Ge0.5 channels grown on Si on insulator. Source and drain areas were formed by BF2+ and As+ ion implantation to doses of 1 × 1013, 1 × 1014, and 1 × 1015 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.