# Suppose a pure Si crystal has 5 x 10^28 atoms/ cubic metre. It is doped by 1 ppm concentration of pentavalent As. caluculate the number of electrons and holes given that ni= 1.5 x 10 ^16 / cubic metre

SAGAR SINGH - IIT DELHI
879 Points
11 years ago

Dear student,

The concentration of dopant introduced to an intrinsic semiconductor determines its concentration and indirectly affects many of its electrical properties. The most important factor that doping directly affects is the material's carrier concentration. In an intrinsic semiconductor under thermal equilibrium, the concentration of electrons and holes is equivalent. That is,

$n = p = n_i.\$

If we have a non-intrinsic semiconductor in thermal equilibrium the relation becomes:

$n_0 \cdot p_0 = n_i^2\$

where n0 is the concentration of conducting electrons, p0 is the electron hole concentration, and ni is the material's intrinsic carrier concentration.