Hydrogenated amorphous silicon alloy films were formed by ionized‐cluster beam deposition of silicon in relatively low gas pressure of hydrogen, in a range of 10−5–10−4Torr. Films with optical band gap of 1.3–1.9 eV could be formed. Effective hydrogenation seems to be due to the enhanced adatom migration effect and to the kinetic and the ionic charge effects of the clusters which are characteristics of the ionized cluster beam deposition. For doped film deposition, hydrogen gas mixed with phosphine or diborane was used. By this method, puren‐ andp‐type films could be reproducibly formed at practical deposition rates by changing gas flow into the deposition chamber. The deposited films have good adhesion and show smooth surface and thermally stable characteristics. Thep‐i‐ndiodes formed by this method showed good performance.