What is a PN junction?

A PN junction has rectifying current–voltage (I–V or IV) characteristics as shown in Fig. 4–2. As a device, it is called a rectifier or a diode. The PN junction is the basic structure of solar cell, light-emitting diode, and diode laser, and is present in all types of transistors. In addition, PN junction is a vehicle for studying the theory

What is the breakdown mechanism of a p-n junction?

The breakdown mechanism of a p-n junction is either the Zener effect (tunnelling) or avalanche (impact ionization). The Zener effect is typical of abrupt junctions with extremely heavy doping, while avalanche breakdown is more common in lightly doped or graded junctions.

How can a PN junction be fabricated?

As illustrated in Fig. 4–1, a PN junction can be fabricated by implanting or diffusing (see Section 3.5) donors into a P-type substrate such that a layer of semiconductor is converted into N type. Converting a layer of an N-type semiconductor into P type with acceptors would also create a PN junction.

How a photon is generated in a PN junction recombine?

Photons are generated when the electrons and holes injected by the PN junction recombine. and a hole recombine. The photon generation process, called radiative recombination, is straightforward and fast in direct-gap semiconductors with nanosecond lifetime.

What is the space-charge region in a pn-junction?

The p and n regions act as the plates of a capacitor, and the space-charge region acts as the dielectric. Thus, the pn-junction in reverse-bias has an effective capacitance, called transition or depletion capacitance.

What devices are based on the PN junction?

Several other useful and even more interesting devices are also based on the PN junction. They are all optoelectronic devices. The first is the solar cell. Commonly made of silicon, solar cells, also known as photovoltaic cells, can covert sunlight to electricity with 15 to 30% energy efficiency.