Intervalley mixing versus disorder in heavily doped n -type silicon

The role of intervalley mixing in the metallic regime of heavily doped n-type silicon is studied in connection with band-gap reduction. The effects of intervalley mixing are found to depend on the arrangement of donors. For a random system, intravalley scattering processes are found to dominate, while intervalley scattering leads only to minor corrections. If the donors are assumed to be ordered, as in recent work, an opposite situation is obtained.