The Relation Between Precursor Gas Flows,Thickness Dependent Material Phases, andOpto-Electrical Properties of Dopeda/nc-SiOX≥0:H Films

Abstract

Doped layers are a determining factor for the performance of
photovoltaic devices such as silicon heterojunction and thin film
silicon solar cells. The material properties of doped hydrogenated
amorphous/nanocrystalline silicon-oxide (a/nc-SiO
X≥0
:H) films processed by plasma-enhanced chemical vapor deposition
generally exhibit a tradeoff between optical and electrical performance.
The optoelectrical properties are the result of different material
phases in these heterogeneous films, such as hydrogenated amorphous
silicon and silicon-oxide tissue, nanocrystalline silicon grains, their
corresponding fractions and extent of doping. In this article, all the
precursor gas flows are varied to achieve a wide range of doped a/nc-SiO
X≥0
:H phases. A material phase diagram is introduced to clarify the complex
interplay between processing conditions, dominant growth mechanisms,
a/nc-SiO
X≥0
:H phases, and the resulting optoelectrical properties. In addition, it
is discussed that material properties are strongly dependent on the
thickness of the films, as the mix of different material phases is not
uniform along the growth direction.