Semiconductor Diode

Introduction to Semiconductor Diode

Semiconductors are critical components of contemporary electronic gadgets, serving as the building blocks of these devices. They can act both as insulators and as conductors. Semiconductors are crucial to the effectiveness of electronic devices. Their adaptability allows for developing a wide range of electronic devices to meet a wide range of needs and provide specialised skills.

What is a Semiconductor Diode?

A Semiconductor Diode is a p-n junction with metallic contacts at both ends that allows an external voltage to be applied. It is only capable of conducting electricity in one direction. 

Types of P-n junction diode

Forward biased P-n junction diode 

A diode is said to be forward-biased when the external voltage applied across the semiconductor diode is used so that the p-side is linked to the battery’s positive terminal, and the n-side is connected to the negative terminal. 

The total charge formed at the p-n junction is called barrier voltage, barrier potential or junction barrier. The height of the barrier lowers as the diode’s built-in voltage and the depletion area’s breadth both decrease in this case. The total voltage of the barrier is determined to be V0-V in this case. 

V0= Initial voltage 

V = Final voltage 

The symbol V0-V shows the difference between the built-in and applied potentials. When a low voltage is applied, only a limited number of current carriers can pass across the junction. Increasing the applied potential by a significant amount will result in a greater decrease in the barrier height and, as a result, an increase in the number of current carriers crossing the junction. In the forward bias case, when voltage is applied from p to n, the length of depletion starts decreasing, due to the electric potential of the battery. 

Reverse biased P-n junction diode

Reverse bias occurs when the battery’s positive terminal is connected to the diode’s n-side. The negative terminal is linked to the diode’s p-side. That is, an external voltage is applied across the semiconductor diode in reverse direction

When an external voltage is placed across the diode, the total voltage barrier increases (V0+V). 

V0 = Initial voltage 

V = Final voltage 

The depletion zone has also become more comprehensive. Consequently, the movement of carriers from one side of the diode to the other is significantly reduced. All of the electrons that emerge from the N side of the semiconductor will be guided in the direction of the battery’s positive terminal. The holes will be pushed away from the junction with the negative terminal connected.

V-I characteristics of P-n junction diode

The relationship between the voltage across the junction and the current through the circuit defines the Volt-Ampere (V-I) characteristics of a P-n junction diode.

Voltage is usually measured along the x-axis, while current is measured along the y-axis.

From the graph, it can be seen that the diode has three distinct modes of operation, which are as follows:

• Zero bias
• Forward bias
• Reverse bias
• Because there is no external voltage provided while the p-n junction diode is operating at zero bias. The potential barrier at the junction is assumed to be closed, preventing current from flowing through the device.
• During the biasing forwarding operation of the p-n junction diode, the positive terminal of the external voltage is linked to the p-type, and the negative terminal is connected to the n-type of the device. A reduction in the potential barrier occurs when the diode is placed in this way. When the voltage applied to silicon diodes is 0.7 V and the voltage applied to germanium diodes is 0.3 V, the potential barriers collapse and current flows.
• When the diode is in forwarding bias, the current progresses slowly, and the curve that appears when the voltage supplied to the diode exceeds the potential barrier is non-linear. When the diode is in reverse bias, the current increases rapidly. Once the diode has passed over the potential barrier, it usually behaves. The curve climbs swiftly as the external voltage increases, resulting in a linear curve in the output voltage.
• As long as the PN junction diode is under negative bias, the p-type is linked to the negative terminal of the external voltage, and the n-type is connected to the positive terminal of the external voltage. As a consequence, the likelihood of encountering a block has increased. For a brief time, reverse saturation current occurs due to minority carriers at the interface.

Semiconductor Diode in a Variety of Applications

The following are some examples of how semiconductor diodes are used:

• A rectifier diode is a semiconductor device used to rectify alternating current.
• The Zener diode is an electrical device used to stabilise current and voltage in electronic circuits.
• The photodiode performs the function of a photodetector.
• A switching diode is a device used to transition between two different states quickly.
• The infrared light spectrum is emitted by LEDs, which are electronic devices.
• Using a variable capacitance diode while applying voltage in reverse bias is an excellent choice.

Conclusion

The P-n junction diode, which ranks third in popularity behind resistors and capacitors, is one of the most extensively used electrical components. The P-n junction diode is the most fundamental kind of semiconductor diode. It is utilised in various rectification applications for current levels, both large and small, and for high and low voltage levels. This semiconductor device has a wide range of applications in all types of electronic circuit designs, including power supplies.

The P-n junction has the essential feature of only allowing electrons to travel in one direction, which is valuable. Because current is made up of a flow of electrons, the current is only permitted to travel in one way across the structure, and it is prevented from flowing in the other direction across the junction.