Highly Stable a-Si:H Films Deposited by Using Multi-Hollow Plasma Chemical Vapor Deposition

Hydrogenated amorphous silicon (a-Si:H) films of high stability against light exposure have been deposited by using a newly developed multi-hollow plasma chemical vapor deposition (CVD) method. Films deposited in the upstream region in the multi-hollow plasma CVD reactor are a-Si:H films without incorporating a-Si:H nano-particles (clusters), while those in the downstream region are a-Si:H films with incorporating clusters. A-Si:H films without clusters have a low initial defect density of 5 ×10 15 cm -3 and keep the value even after 100 h exposure of intense light intensity of 240 mW/cm 2 , whereas a-Si:H films with clusters show a significant increase in defect density from its initial value of 5 ×10 15 cm -3 to 2 ×10 16 cm -3 after 100 h light exposure. These results indicate that suppression of clusters incorporated into films is the key to realizing highly stable a-Si:H films.