Magnetoresistance in Heavily Dopedn-Type Silicon

The magnetoresistance effect has been investigated in $n$-type silicon at 4.2, 77, and 300°K. At 77 and 300°K, the low-field magnetoresistance coefficients have been evaluated in the impurity concentration range from approximately 1×${10}^{15}$ to 1×${10}^{20}$ ${\mathrm{cm}}^{-3\mathrm{}}$. At 300°K, the symmetry relation among the coefficients found in pure silicon is obeyed at all impurity concentrations, while at 77°K, the symmetry relation is fulfilled only up to impurity concentrations of 1×${10}^{18}$ ${\mathrm{cm}}^{-3\mathrm{}}$. The mobility anisotropy has been evaluated from the low-field coefficients in the impurity concentration ranges where the symmetry relation is obeyed. At 4.2°K, the magnetoresistance effect is negative and tends toward saturation with increasing magnetic field strength for impurity concentrations greater than 5×${10}^{18}$ ${\mathrm{cm}}^{-3\mathrm{}}$. Below this concentration, a large positive magnetoresistance is observed and the change in sign is correlated with the appearance of an impurity ionization energy.