Structural and electrical properties of poly-SiGe thin films prepared by reactive thermal CVD

Abstract

Polycrystalline thin films of Si ×Ge (0.95≥×≥0.05, poly-SiGe) were prepared on SiO 2 and glass substrates by thermal chemical vapor deposition (CVD) from Si 2H 6 and GeF 4 at 450°C. The Ge-rich films had a high crystallinity owing to the direct nucleation of crystallites on the substrates. The crystallinity of Si-rich films, however, depended on the growth rate, and the direct nucleation was achieved at smaller growth rates, leading to improvement of the crystallinity. All the films were p-type regardless of film composition, whose carrier concentration decreased from 10 18 cm −3 to 10 12 cm −3, and the Hall mobility from 100 cm 2/Vs to 1 cm 2/Vs with an increase in the Si content in the films. The Hall mobility was improved up to 8 cm 2/Vs in the film prepared at a growth rate of 3.6 nm/min.