Question

The number of silicon atoms per m³ is 5 × 10^28. This is doped simultaneously with 5 ×10²² atoms per m³ of Arsenic and 5 × 10²⁰ per m³ atoms of Indium. Calculate the number of electrons and holes. Given that ni= 1.5 × 10¹⁶ m⁻³. Is the material n-type or p-type?

Answer 1

Number of silicon atoms, N = 5 × 10²⁸ atoms/m³
Number of arsenic atoms, n_As = 5 × 10²² atoms/m³
Number of indium atoms, n_In = 5 × 10²⁰ atoms/m³
Number of thermally-generated electrons, n_i = 1.5 × 10¹⁶ electrons/m³ Number of electrons, ne = 5 × 10²² − 1.5 × 10¹⁶ ≈ 4.99 × 10²²

Therefore, the number of electrons is approximately 4.99 × 10²² and the number of holes is about 4.51 × 10⁹. Since the number of electrons is more than the number of holes, the material is an n-type semiconductor.