Mechanisms Influencing "Hot-Wire" Deposition of Hydrogenated Amorphous Silicon
Intrinsic hydrogenated amorphous silicon (a-Si:H) has been deposited using a hot tungsten filament in pure silane to drive the deposition chemistry--the ''hot-wire'' deposition method. The electronic and infrared properties of the film have been measured as a function of deposition parameters, leading to three principal conclusions. First, to obtain a high quality material, the Si atoms evaporated from the filament (distance L from the substrate) must react with silane (density ns) before reaching the substrate; this requires nsL greater than a critical value. Second, radical-radical reactions cause deterioration of film properties at high values of G(nsL),3 where G is the film growth rate; this requires G(nsL)3 less than a critical value. Finally, the film quality is a function of G, and as G is increased the substrate temperature must be correspondingly increased to obtain high film quality. By optimizing these parameters, we have produced films with excellent electronic properties (e.g., ambipolar diffusion length >200 nm) at >5 nm/s deposition rate. Based on these insights, formulas are also given for optimizing film properties in multiple-filament geometries and in diluted silane.
- Research Organization:
- National Renewable Energy Laboratory (NREL), Golden, CO.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC36-99GO10337
- OSTI ID:
- 915277
- Journal Information:
- Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 4, 15 August 1997 Vol. 82; ISSN JAPIAU; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
Similar Records
Low hydrogen content, high quality hydrogenated amorphous silicon grown by hot-wire CVD
Production of high-quality amorphous silicon films by evaporative silane surface decomposition