Electronic properties and microstructure of undoped, and B- or P-doped polysilicon deposited by LPCVD

Abstract

In this paper, we present some results on the electrical and optical properties of thin layers of polysilicon obtained by LPCVD in a sector reactor [1]. This reactor is representative of annular reactor, in which a large batch can be processed (total area up to 150 m 2). The layers are either undoped, or in situ doped with boron or phosphorus. The optical constants were determined by the analysis of absorption and transmission spectra. We show that the absorption coefficient of the layers (doped or undoped) enable a total absorption in the visible range with a thickness of 10 μm. We then show that uniform growth rate can be obtained on 100 cm 2 substrates, with a value of 200 A ̊ mn at 660°C for undoped or P-doped silicon, and 700 A ̊ mn for B-doped silicon. The carrier concentrations ranges between 1 × 10 17 and 1 × 10 20cm −3, which allows the realization of doping gradient during the process and potentially good solar cells with a high productivity.