A PN junction diode is formed by combining a P type semiconductor with N type semiconductor. It has the property of offering a low resistance to current flow in one direction and is the main components used in rectifying circuits. PN junction diodes are mainly manufactured using Germanium or Silicon semiconductor material.
Summary of Junction Diode
The PN junction region of a Junction Diode has the following important characteristics:
1). Semiconductors contain two types of mobile charge carriers, Holes and Electrons.
2). The holes are positively charged while the electrons negatively charged.
3). A semiconductor may be doped with donor impurities such as Antimony (N-type doping), so that it contains mobile charges which are primarily electrons.
4). A semiconductor may be doped with acceptor impurities such as Boron (P-type doping), so that it contains mobile charges which are mainly holes.
5). The junction region itself has no charge carriers and is known as the depletion region.
6). The junction (depletion) region has a physical thickness that varies with the applied voltage.
7). When a diode is Zero Biased no external energy source is applied and a natural Potential Barrier is developed across a depletion layer which is approximately 0.5 to 0.7v for silicon diodes and approximately 0.3 of a volt for germanium diodes.
8). When a junction diode is Forward Biased the thickness of the depletion region reduces and the diode acts like a short circuit allowing full current to flow.
9). When a junction diode is Reverse Biased the thickness of the depletion region increases and the diode acts like an open circuit blocking any current flow, (only a very small leakage current).