HC Verma Chapter 45 Problem 3

Problem Statement

Conductivity of pure semiconductor = 4e-4 ohm-1m-1. Electron mobility = 0.13 m2/Vs, hole mobility = 0.05 m2/Vs. Find intrinsic carrier concentration.

Key Concepts

Conductivity, carrier mobility

Relevant Formulas

sigma = n_i * e * (mu_e + mu_h)

Step-by-Step Solution

n_i = sigma/[e(mu_e + mu_h)] = 4e-4/[1.6e-19 x 0.18] = 4e-4/2.88e-20 = 1.39e16 m-3.

Final Answer

n_i = 1.39e16 m-3

Tips and Tricks

Both electrons and holes contribute; sum their mobilities.

Common Mistakes

Always use SI units. Check energy conservation accounts for all forms.