extrinsic conductivity

Extrinsic conductivity refers to the electrical conductivity of a semiconductor that has been modified by deliberately adding impurities, known as dopants. Pure semiconductors, like silicon, have limited conductivity at room temperature. However, by introducing specific dopant atoms, their electrical properties can be significantly altered.1234

There are two main types of extrinsic semiconductors:

• n-type semiconductors: Created by adding dopants with more outer electrons than the semiconductor material (e.g., phosphorus or arsenic in silicon). These extra electrons become free charge carriers, making the semiconductor negatively charged.156
• p-type semiconductors: Created by adding dopants with fewer outer electrons than the semiconductor material (e.g., boron or indium in silicon). This creates "holes" in the atomic structure, which act as positively charged carriers that can move through the crystal.156

This controlled modification of conductivity through doping is fundamental to the creation of electronic devices like diodes and transistors.73