ELECTRONIC-PROPERTIES AND MICROSTRUCTURE OF UNDOPED, AND B-DOPED OR P-DOPED POLYSILICON DEPOSITED BY LPCVD

In this paper, we present some results on the electrical and optical p roperties of thin layers of polysilicon obtained by LPCVD in a sector reactor [1]. This reactor is representative of annular reactor, in whi ch a large batch can be processed (total area up to 150 m(2)). The lay ers are either undoped, or in situ doped with boron or phosphorus, The optical constants were determined by the analysis of absorption and t ransmission spectra. We show that the absorption coefficient of the la yers (doped or undoped) enable a total absorption in the visible range with a thickness of 10 mu m. We then show that uniform growth rate ca n be obtained on 100 cm(2) substrates, with a value of 200 Angstrom/mn at 660 degrees C for undoped or P-doped silicon, and 700 Angstrom/mn for B-doped silicon. The carrier concentrations ranges between 1 x 10( 17) and 1 x 10(20) cm(-3), which allows the realization of doping grad ient during the process and potentially good solar cells with a high p roductivity.