Photochemical vapor deposition of undoped and n-type amorphous silicon films produced from disilane

Abstract

Hydrogenated amorphous silicon films have been deposited by mercury photosensitized decomposition (photochemical vapor deposition: photo-CVD) of disilane at a substrate temperature below 300 °C. The structural and optical properties of undoped films are very similar to those of films deposited by rf glow discharge decomposition. The electronic property measurement shows that the conductivity strongly depends on the substrate temperature during deposition. The photoconductivity reaches 5.7×10−3 (Ω cm)−1 (AM1,100 mW/cm2) at a substrate temperature of 200 °C. The dark conductivity is 10−6–10−8 (Ω cm)−1 and the Fermi level is located near the middle of the gap. n-type doping has been also achieved by adding phosphine as an impurity to disilane. Furthermore, a p-i-n a-Si solar cell was fabricated using photo-CVD undoped and P-doped films. The initial cell showed a conversion efficiency of 4.39% under AM1 insolation.