Effect of post-deposition treatments on the hydrogenation of hot-wire deposited amorphous silicon films

✍ Scribed by K. F. Feenstra; P. F. A. Alkemade; E. Algra; R. E. I. Schropp; W. F. van der Weg

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 167 KB
• Volume: 7
• Category: Article
• ISSN: 1062-7995
• DOI: 10.1002/(sici)1099-159x(199909/10)7:5<341::aid-pip261>3.0.co;2-4

✦ Synopsis

The eect of dierent post-deposition treatments on the structure of Hot-Wire (HW) deposited intrinsic a-Si:H thin ®lms is investigated. These treatments are applied in order to rehydrogenate the top region of the ®lm, which, due to the high deposition temperatures of these ®lms, becomes depleted of hydrogen. Using secondary ion mass spectroscopy (SIMS) for measurement of the hydrogen pro®les and Raman spectroscopy measurements to investigate the hydrogen bonding con®guration at the surface, we were able to determine the eect of the dierent treatments on the ®lms. We show that the hydrogen pro®le in the subsurface region is not a result of the out-diusion of hydrogen while the sample is cooled down after the deposition, but develops during the growth of the ®lm. The most eective bulk rehydrogenation is achieved with an atomic hydrogen treatment, for which we determined a diusion coecient for atomic hydrogen of 7 Â 10 À14 cm 2 s À1 at 4308C. Rapid cooling and a hydrogen plasma treatment are shown to result in an improved top surface hydrogenation of the intrinsic ®lm. Despite the dierences in top surface hydrogenation of the intrinsic ®lms, application of the treatments in real n-i-p solar cell devices did not show an improvement in the cell properties. We attribute this to the existence of defects deeper in the bulk of the intrinsic layer or at the n/i-interface, being the dominating eect that limits the cell performance.