Electric Conduction in Phosphorus Doped Silicon at Low Temperatures

The impurity conduction in phosphorus doped n -type silicon has been investigated at temperatures between 1.1°K and 300°K. The samples ranged in concentration of excess donors from 1.2.10 18 to 2.5.10 20 cm -3 . A metallic type impurity conduction and a negative magnetoresistance are observed in samples containing higher than 4.10 18 cm -3 excess donors. An intermediate type impurity conduction is observed in samples containing from 1.7.10 18 to 4.10 18 cm -3 excess donors. In metallic samples with donor concentration higher than 6.10 18 cm -3 , the resistivity increases monotonically with temperature T up to the Fermi degeneracy temperature T D of respective samples according to a simple formula, ρ( T )=ρ(4.2^°K)[1+ A ( T / T D ) B ], where A and B are constants.