Optimisation of doped microcrystalline silicon films deposited at very lowtemperatures by hot-wire CVD

In this paper we present new results on doped mu c-Si:H thin films deposite d by hot-wire chemical vapour deposition (HWCVD) in the very low temperatur e range (125-275 degrees C). The doped layers were obtained by the addition of diborane or phosphine in the gas phase during deposition. The incorpora tion of boron and phosphorus in the films and their influence on the crysta lline fraction are studied by secondary ion mass spectrometry and Raman spe ctroscopy, respectively. Good electrical transport properties were obtained in this deposition regime, with best dark conductivities of 2.6 and 9.8 S cm(-1) for the p- and n-doped films, respectively. The effect of the hydrog en dilution and the layer thickness on the electrical properties are also s tudied. Some technological conclusions referred to cross contamination coul d be deduced from the nominally undoped samples obtained in the same chambe r after p- and n-type heavily doped layers. (C) 2000 Elsevier Science S.A. All rights reserved.