Drift velocity of electrons and holes and associated anisotropic effects in silicon

Abstract

The drift velocity of electrons and holes in high purity silicon has been measured, with the time of flight technique, as a function of electric field (0·1–50 KV/cm) at several temperatures between 77 and 300°K. By applying the electric field parallel to the <111> and <100> crystallographic directions, an evident longitudinal anisotropy effect has been found for the drift velocity of electrons and also, for the first time, for the drift velocity of holes. At high values of the electric field a saturation drift has been found for the electrons at the temperatures considered in these experiments. On the contrary, no saturation has been attained for holes, even at the highest applied electric fields. The ohmic mobility has been measured between 77 and 300°K for electrons and between 160 and 300°K for holes. When a comparison is possible, our results are in good agreement with other experimental results found in the literature. A qualitative theoretical interpretation of the effects observed is given.