Semiconductor Electronics: Materials, Devices and Simple Circuits — Important Questions

Phosphorus (P), Arsenic (As), Antimony (Sb)

N-type semiconductors are created by doping with pentavalent (5 valence electrons) impurities like P, As, and Sb. These donate extra electrons. Trivalent elements like B, Al, In create p-type semiconductors.

Majority: holes, Minority: electrons

In p-type semiconductors, doping with trivalent impurities creates more holes than electrons. Holes become majority carriers while electrons are minority carriers (nh >> ne).

Electrons diffuse from n to p region, Holes diffuse from p to n region, A depletion region is formed, An electric field develops across the junction

At p-n junction formation, diffusion creates a depletion region with fixed charges, establishing an electric field. At equilibrium, diffusion and drift currents balance, so no net current flows.

0.7 V

Silicon diodes have a threshold voltage of approximately 0.7 V in forward bias. Germanium diodes have a lower threshold of about 0.2 V. This is the minimum voltage needed for significant current flow.