N-Type and P-Type Semiconductors

• Semiconductive materials do not conduct current well and are of limited value in their intrinsic state;
• This is because of the limited number of free electrons in the conduction band and holes in the valence band;
• Intrinsic silicon (or germanium) must be modified by increasing the number of free electrons or holes to increase its conductivity and make it useful in electronic devices;
• This is done by adding impurities to the intrinsic material;
• Two types of extrinsic (impure) semiconductive materials, n-type and p-type, are the key building blocks for most types of electronic devices;

 

• Since semiconductors are generally poor conductors, their conductivity can be drastically increased by the controlled addition of impurities to the intrinsic (pure) semiconductive material;
• This process, called doping, increases the number of current carriers (electrons or holes);
• The two categories of impurities are n-type and p-type;