Preparation and Properties of High-Quality a-Si Films with a Super Chamber : Separated Ultra-High Vacuum Reaction Chamber

Abstract

A separated ultra-high vacuum (UHV) reaction chamber system, called the super chamber, has been newly developed. A background pressure of 10 -9 Torr was obtained, and the impurity concentrations of oxygen, nitrogen and carbon in an a-Si film fabricated in the super chamber were 2×10 18 cm -3 , 1×10 17 cm -3 , and 2×10 18 cm -3 , respectively. The space charge density and the ESR spin density of the a-Si film were 5×10 14 cm -3 and 2×10 15 cm -3 , respectively. These values were much lower than those for films fabricated in a conventional chamber. The ratio of the light-induced degradation in the photoconductivity of the a-Si film was also small compared with that of conventional a-Si films. A conversion efficiency of 11.7% was obtained for a glass/textured TCO/pin/Ag a-Si solar cell, whose i-layer was fabricated in the super chamber.