Deposition of Device Quality, Low H Content a-Si:H by the Hot Wire Technique

Abstract

ABSTRACTWe report measurements of the Urbach edge, optical bandgap, and ambipolar diffusion length on a series of hydrogenated amorphous silicon (a-Si:H) films deposited by hot-wire-assisted chemical vapor deposition (HW). We compare the properties of these films to those of a series of a-Si:H films deposited by the traditional radio frequency (rf) glow discharge (GD) technique, where we varied the substrate temperature to change the bonded H content (CH). We show for the first time that, as CH is decreased below the value traditionally associated with device quality GD a-Si:H (∼10 at.%), the electronic properties of the GD films deteriorate in the traditional manner while those for the HW samples remain device quality. Properties of these low CH HW samples will be presented and compared to those of GD films containing comparable CH. Because several indications exist that the structure of the HW films is different than that of the GD films, Raman and Small Angle X-Ray Scattering (SAXS) measurements are presented to illustrate structural differences.