Semiconductors are materials that have conductivity values between those of metals and non-metals. Semiconductors may be further classified into two categories:

1. a) Semiconductors of the p-type (which are positively charged)
2. b) Semiconductors of the n-type (which are negatively charged)

Semiconductor diodes are the p-n junction diode formed by the doping of elements of group 14 with 15. It is a two-terminal device that only conducts current in a single direction. The term “p-n junction diode” refers to diodes formed by an interface or boundary between two distinct types of the semiconductor materials present within a semiconductor, namely the p-type and the n-type.

When it comes to semiconductors, the p-side (positive side) has more holes than electrons, whereas the n-side (negative side) has more electrons than holes; p-n junctions are created in semiconductors during the doping process.

When a p-n junction is coupled to an external voltage source, such as a battery, the result is a semiconductor diode.

Types of Semiconductors diodes

The semiconductor diodes may be categorised as either a forward-bias or a reverse-bias semiconductors diode, depending on how the external voltage is provided to the device.

• Semiconductor diode Forward Bias: The voltage applied across the p-n junction diode is such that the p side of the junction is linked to the battery’s positive terminal, and the n side of the junction is connected to the battery’s negative terminal; this is known as the p-n junction diode configuration. As a result, the connection has a forward bias. 

In the forward biassed semiconductor diode, the free electrons will be driven in front of junctions by the negative corner of the battery, and the holes will be pushed in front of junctions by the positive end of the semiconductor where they will combine. 

Nevertheless, when free electrons flow out of the battery, they will reach the N area, and the valence electrons will depart the P region, resulting in a current flow in the battery.

• Semiconductor diode Reverse bias: When the battery’s positive terminal is linked to the n side of the junction, and the battery’s negative terminal is connected to the p side of the junction, the junction is said to be reverse-biassed. All electrons that arise from the semiconductor’s N side will be directed toward the battery’s positive end. 

The holes will be pushed away from the junction with the negative terminal attached. Because the holes and electrons never make contact at the junction, this design causes a blockage in the passage of current; as a result, the length of the depletion region or depletion layer is increased. As can be seen, most of the current flows in the same direction as the bias. 

Rather than that, there is a reversal of the current flow in this situation due to the existence of minority charge carriers. The ideal resistance of the semiconductor diode reverse bias is infinite.

Things to remember about semiconductor diode

Depletion layer: The region of a P-N junction diode where no mobile charge carriers are present is known as the depletion region or depletion layer. The depletion layer functions as a barrier, preventing electrons from the n-side and holes from the p-side from interacting with one another.

Zener Breakdown: Increasing the reverse bias to a significant degree makes the electric field much larger, resulting in a high number of electrons and holes being generated. The breakdown is referred to as a Zener breakdown.

Potential Barrier: A barrier is created by the electric field produced in the depletion zone due to the presence of opposite immobilised charge carriers. External energy must be supplied in order for electrons to cross through the electric field barrier. 

This potential differential required by the electrons to pass through this potential difference between the depletion region is referred to as the potential Barrier. It depends upon the type of semiconductor we are using, the kind of material, the amount of doping, and the temperature at which the semiconductor is employed. It is around 0.7V for silicon and 0.3V for germanium.

Applications of the Semiconductor Diode

• Rectifier diode: It is used to rectify alternating current.
• Gunn diode: It is a kind of diode that is used in high-frequency electronics.
• Light Emitting Diode (LED): LEDs are used to emit infrared light and colourful lights.
• Zener diode: In electronic systems, it is used to stabilise current and voltage. For the purpose of providing a reference voltage in the power supply, Zener diodes are often used.
• Photodiode: It is a kind of photodetector used in various detectors in advanced optical instruments and solar cells.
• Switching diode: It is utilised for high-speed switching applications.
• Tunnel diodes: These are a kind of diode that is employed in the area of negative dynamic resistance.
• Capacitance diode: When a voltage is supplied in a reverse biassed situation, a variable capacitance diode is employed.
• Semiconductor diodes are also employed to execute logic operations in addition to other applications. Logic gates have states that are analogous to the biassed states of semiconductor diodes in both the forward and reverse directions. As a result, diodes are useful in OR, NAND, and AND gates.

Conclusion

Semiconductor diodes are the p-n junction diodes connected to the external electric current sources. In a forward bias semiconductor diode, the battery’s positive terminal is connected to a p-type region of the semiconductor diode, and the n-type region is connected to the battery’s negative terminal. In a reversed bias semiconductor diode, the battery’s negative terminal is connected to the p-type region of the semiconductor diode, and the battery’s positive terminal is connected to the n-type region of the semiconductor. Semiconductor diodes are used in almost all electronic divides from LED, rectifiers, photodiodes, and transformers.