Characterization of Highly Conductive Phosphorus Doped µc-Si:H Films

Abstract

In this work the electro-optical properties of phosphorus doped microcrystalline hydrogenated silicon (µc-Si:H) films as a function of their deposition parameters are investigated.

The films were deposited in a plasma enhanced CVD system. It is observed that their properties are extremely sensitive to the r.f. power density in the studied range of 250 mW/cm² to 500 mW/cm².

Very low resistivitv films were obtained. For a r.f. power density of 500 mW/cm², ρ=5×10^-2 ohm.cm was obtained whilst, for a r.f. power density of 250 mW/cm² a resistivity of ρ=3,7×10² ohm.cm is observed. These results show the sensitivity of the process to small changes in its variable deposition parameters. A low value of 28 meV for the activation energy was obtained with a r.f. power density of 500 mW/cm² which can be due to a large density of microcrystals embedded in the amorphous tissue. The grain crystalline size as estimated from small angle X-Ray scattering experiments is in the range of 70 Å to 120 Å.

This promising material has immediate technological applications and it is believed that the experiments on the way will provide more understanding on the deposition phenomenology.