BAND-GAP TUNING OF A-SI-H FROM 1.55 EV TO 2.10 EV BY INTENTIONALLY PROMOTING STRUCTURAL RELAXATION

Substrate temperature and sequential treatments are used to prepare a- Si:H films with band gaps ranging from 1.55 to similar to 2.1 eV. Low band gap materials were prepared at higher substrate temperature using a sequential process involving the deposition of thin (less than or s imilar to 5 nm) a-Si:H layers followed by an Argon radical (and/or ion ) treatment. Larger band gap materials were prepared at lower substrat e temperatures using a hydrogen chemical annealing process. The series was used to determine the relationship among the deposition condition s, the opto-electronic characteristics, and the atomic bonding structu res in a-Si:H. The band gap is correlated to the total di-hydride cont ent. The local silicon-silicon bonding environments, the hydrogen, and mono-hydride content and the mono-to di-hydride ratio are not well co rrelated to the band gap. Electronic transport is correlated with the local silicon-silicon bonding environment, but not the di-hydride cont ent. (C) 1998 Elsevier Science B.V. All rights reserved.