Synthesis of heavily Ga-doped Si1−xSnx/Si heterostructures and their valence-band-offset determination

Heavily doped Si1−xSnx alloys are strongly desired for next-generation group-IV electronics. A polycrystalline growth study has been conducted on heavily Ga-doped amorphous Si0.9Sn0.1 layers deposited on a tensile-strained Si-on-insulator substrate. P-type conduction and a high Hall hole concentration over 1020 cm−3 are observed for grown Si1−xSnx layers with the initial Ga concentration of 1021 cm−3. In addition, we find that the valence-band offset of the Si1−xSnx relative to Si (ΔEv) is determined by the substitutional Sn content regardless of the hole concentration in the grown layers. Even for the substitutional Sn content less than 5%, a relatively high value of ΔEv (~0.5 eV) could be obtained. These results suggest that with heavily Ga-doped Si1−xSnx alloys could become a p+-source material, which would provide benefits for Si-based tunnel field-effect transistors.