Hydrogenated amorphous silcon germanium Alloys Grown by the Hot-Wire Chemical Vapor Deposition Technique

Published

April 1, 2000

Author(s)

B P. Nelson, Y Xu, D L. Williamsons, B von Roedern, A Mason, S Heck, A. H. Mahan, S F. Schmitt, Alan Gallagher, J Webb, R C. Reedy

Abstract

We successfully grow high quality hydrogenated amorphous-silicon germanium alloys(a: SiGe:II) by the hot-wire chemical vapor deposition (HWCVD) technique using silane and germane gas mixtures. These alloys display electronic properties as good as those grown by (the plasma-enhanced chemical-vapor deposition (PECVD) technique, when comparing materials with)thesame optical bandgaps. However, we grow materials with good electrical properties at high desposition rates-up to 40 /s compared to 1-4 /s for PECVD materials. Our alloys exhibit similar trends with increasing Ge content to alloys grown by PECVD. The defect density, the dark conductivity, and the degree of nanostructural heterogeneity (as measured by small-angle X-ray scattering) all increase with increasing germanium content in the alloy. The nanostructural heterogencity displays a sharp transition between 9 at % and 14 at % germanium. PECVD-grown a SiGe: II alloys exhibit a similar transition at 20 at % Ge. The photoconductivity and the ambipolar diffusion length of the alloys decrease with increasing germanium content. For a fixed silane-to-germane gas ratio, all material properties improve substantially when increasing substrate temperature (T_sub) from 220 C to 375C . Increasing T ^sub^ also narrows the optical bandgap and lowers the hydrogen content in the alloys for the same germane-to-silane gas ratio.

Citation

Journal of the Materials Research Society

Volume

507

Pub Type

Journals

Keywords

hot-wire chemical-vapor deposition (HWCV, hydrogenated amorphous-silicon-germanium, optical bandgap

Citation

Nelson, B. , Xu, Y. , Williamsons, D. , von, B. , Mason, A. , Heck, S. , Mahan, A. , Schmitt, S. , Gallagher, A. , Webb, J. and Reedy, R. (2000), Hydrogenated amorphous silcon germanium Alloys Grown by the Hot-Wire Chemical Vapor Deposition Technique, Journal of the Materials Research Society (Accessed December 6, 2024)