Electronic properties of PECVD hydrogenated amorphous silicon with predominantly monohydride bonding deposited at less than 150°C

PECVD hydrogenated amorphous silicon (a-Si:H) prepared with silane, typically has predominant monohydride bonding only at substrate temperatures above 200°C. Using rf plasma enhanced chemical vapor deposition, we have deposited a-Si:H films at a substrate temperature near 30% using silane diluted with helium, and found that films with dominant monohydride configuration can be deposited without significant substrate heating. As deposited, the films with predominant monohydride bonding show low dark conductivity (10^-9 S/cm) and photoconductivity (20^-7 S/cm at near AM1 illumination). However, annealing the films for 3 hours at 150%, improved the photo to dark conductivity ratio by a factor of 10². These films may be valuable for the fabrication of thin film electronics on low temperature substrates