We report on the electronic properties, stability and hydrogen content of amorphous hydrogenated silicon films (a-Si:H) grown by hydrogen assisted chemical vapour deposition. The dependence of the dark conductivity and photoconductivity, the optical gap, defect density, Urbach energy, microstructure parameter and hydrogen content on substrate temperature, varied in the range 150-350 degrees C, was investigated. As a result, the defect density, determined by the constant photocurrent method, reaches a minimum value of 5 x 10(15) cm(-3) at 240 degrees C with an Urbach energy of 45 meV and a hydrogen content of 5 at.%, obtained from analysis of the corresponding IR spectra. After 36 h light soaking, performed with a xenon flash lamp, the defect density is increased to a value of 5 x 10(17) cm(-3). The observed dependence of the material properties on substrate temperature is discussed in the light of existing growth models.