Hydrogenated amorphous silicon films prepared at high substrate temperature: Properties and light induced degradation

Of the different deposition parameters, the substrate temperature Ts has a profound effect on the microstructure and optoelectronic properties of hydrogenated amorphous silicon (a-Si:H). A detailed study was done to evaluate a-Si:H materials deposited at high substrate temperatures (≥325 °C). Their characteristics and nature of light induced degradation were compared to a-Si:H deposited at 200 °C. Electrical properties were studied with coplanar electrode structure as well as on Schottky barrier devices. Absorption measurements in the visible and infrared regions and spin-density measurements were carried out. For high Ts (≥325 °C) the presence of acceptorlike defects are indicated in addition to the neutral dangling bonds. Annealing recovery from the light soaked state is slower as compared to a film deposited at 200 °C. The results have been discussed in connection with the role of hydrogen motion in the annealing of light induced defects.