The effects of the phosphorus incorporation on physical, chemical, optical and electric properties of phosphorus-doped hydrogenated amorphous silicon thin films (a-Si:H(P)) are presented. Doping was carried out from the use of a nontoxic phosphorus liquid source based on hydrocarbons (trimethylphosphine: TMP, (P (CH₃) introduced into the deposit chamber by using hydrogen as carrying gas.

The a-Si:H films (0.7-1.0 mm thick) were deposited by the DC magnetron sputtering of a silicon target under hydrogen and argon plasma at various TMP partial pressures between 0 to 9.10^-5 mbar. The a-Si:H(P) were characterized by secondary ion mass spectrometry (SIMS), infrared absorption, optical transmission and electrical conductivity measurements.
The infrared   absorption at 670 cm^-1 can be attributed to the P-H bonds. The effect of TMP partial pressure can be observed through the broadening of the 2000 cm^-1 band and a displacement towards the high frequencies. The phosphorus incorporation in a-Si:H matrix was confirmed by secondary ion mass spectrometry (SIMS) measurements.

Optical transmission measurements are used in order to determine the refractive index n_S and the optical gap E_T.  The increase of E_T can be explained by carbon/silicon alloy effect and the variation in refractive index is indicative of material structure change.

The effect of annealing temperature on electrical conductivity was also studied. The results concerning the variation of electrical conductivity under darkness and photoconductivity, respectively σ_d and σ_ph, according to the annealing temperature T_a clearly evidenced an increase in conductivity with T_a in the range of 130 - 225° C. The increase of conductivity with annealing can be explained by the increase in the doping effectiveness through the activation of the phosphorus atoms in the silicon matrix. The decrease of E_a can be related to the shift of the Fermi level towards the conduction band due to phosphorus doping.

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