Anomalous grain boundary and carrier transport in cat-CVD poly-Si films

Abstract

Polycrystalline silicon (poly-Si) films are obtained at temperatures less than 400°C by catalytic chemical vapor deposition (cat-CVD) method, often called `hot-wire CVD' method. Structural properties of the cat-CVD poly-Si films are studied by Raman spectroscopy and high resolution transmission electron microscopy, along with carrier transport properties measured by the Van der Pauw method. It is found that the cat-CVD poly-Si films have a microstructure which consists of columnar crystalline grains with tens of nanometers diameter and a few nm thick amorphous layers surrounding the columnar grains. It is also found that the Hall mobilities of some samples are several-tens cm 2/V s and the barrier heights at the grain boundaries become the order of 0.01 eV or less. These good carrier transport properties appear dependent on the grain boundary structure of the cat-CVD poly-Si films.