The PN junction region of the Junction Diode has the following significant characteristics:
- Semiconductors contain two types of mobile charge carriers, Electrons and Holes.
- The electrons negatively charged while holes are positively charged.
- A semiconductor can be doped with donor impurities like Antimony (N-type doping), so that it contains mobile charges which are the primarily electrons.
- A semiconductor can be doped with the acceptor impurities such as Boron (P-type doping), so that it contains mobile charges which are majorly holes.
- The junction region itself has no charge carriers and is called as the depletion region.
- The junction region has physical thickness which varies with the applied voltage.
- When the diode is Zero Biased no external energy source is applied and a natural Potential Barrier is developed across the depletion layer which is about 0.5 to 0.7v for silicon diodes and about 0.3 of a volt for germanium diodes.
- When the junction diode is Forward Biased thickness of the depletion region reduces and the diode acts as a short circuit allowing full current to flow.
- When the junction diode is Reverse Biased thickness of the depletion region increases and the diode behaves like an open circuit blocking any current flow, (only a small leakage current).