Question

A pure silicon crystal has 6 × 10²⁸ atoms. It is doped by 1 PPM concentration of antimony. Calculate

the number of holes. Given, nᵢ = 1.2 × 10¹⁶ / m³.

(a) 3.4 × 10⁹ m⁻³ (b) 3.6 × 10⁹ m⁻³

(c) 2.4 × 10⁹ m⁻³ (d) 2.8 × 10⁹ m⁻³​

Answer 1

Answer:

(c) 2.4 × 10⁹ m⁻³

Explanation:

• Given that a pure silicon crystal has 6 × 10²⁸ atoms

1 PPM means 1 part per 10⁶

     Now number of electrons are = 6 × 10²⁸ / 10⁶ = 6 × 10²² electrons

We have a formula ,

                $n_en_h = n_i^{2} \\\\n_i = 1.2 * 10^{16} /m^3 \\\\Now, \\ \\ n_e = 6 * 10^{22} electrons\\\\ by \ putting \ the \ values \ \\ \\ 6 * 10^{22} * n_h = ( 1.2 * 10^{16})^2\\\\=> n_h = \frac{ 1.44 * 10^{32}}{ 6 * 10^{22}} \\\\=> n_h = 2.4 * 10 ^9 \ holes (c) \ (Ans.)$  

            Hope it helps mate

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