Conduction mechanisms in crystallized silicon films on molybdenum substrates

Hydrogenated amorphous silicon films deposited on molybdenum sheet metal substrates have been crystallized by thermal annealing at 850°C for 4 hours in a nitrogen atmosphere. X-ray diffraction and scanning electron microscopy results indicated that the average grain size in the crystallized films was approximately 200angstrom. Palladium contacts were fabricated and the resulting Pd/Si/Mo structures were electrically characterized. Current-voltage-temperature measurements for phosphorus doped and undoped annealed samples resulted in a J ∝ V² characteristic consistent with space-charge-limited current. Using this data, mobility as a function of temperature from 100K-300K was obtained. In phosphorus doped samples, the mobility appeared to be limited by energy barriers at the grain boundaries. In undoped samples, a σ ∝ T^{- 1/2} exp(-b/T ^1/4 ) temperature dependence consistent with variable-range hopping conduction was observed.