Doping and electrical characteristics of in situ heavily B-doped Si 1− xGe x films epitaxially grown using ultraclean LPCVD

Abstract

Doping and electrical characteristics of in situ heavily B-doped Si 1− x Ge x ( 0.15 < x < 0.80) films epitaxially grown on Si(110) were investigated. The epitaxial growth was carried out at 550 °C in a SiH 4-GeH 4-B 2H 6-H 2 gas mixture by using an ultraclean hot-wall low pressure chemical vapor deposition (LPCVD) system. With increasing B 2H 6 partial pressure, the deposition rate decreased only at the higher GeH 4 partial pressure, and the B concentration ( C B ) in the film increased proportionally up to 10 22 cm −3. The Ge fraction scarcely changed with the B 2H 6 addition. The carrier concentration was nearly equal to cb up to about 2 × 10 20 cm −3, and it tended to be saturated at around 5 × 10 20 cm −3 at C B < ~ 10 22 cm −3 . In other words, electrically inactive B increased with increasing C B above 2 × 10 20 cm −3. The resistivity decreased with increasing carrier concentration at c b <~ 10 22 cm −3 and was influenced by alloy scattering. Discrepancy of the lattice constants from Vegard's law was observed at higher cb in the order of 10 20 cm −3 and above, which corresponded with the saturation of the carrier concentration.