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.