Electronics-semiconductor devise | Semiconductor device example | Semiconductor Devices: Definition, construction, Types, Application

Electronics-semiconductor device

P-N junction diode

In an N-type 

the material the electron is called the majority carrier and the hole of the minority career.

In a P-type

For semiconductor device example material the hole is the majority career and the electron is the minority career. The N- and P-type materials represent the basic building blocks of semiconductor devices.

what are semiconductors used in the semiconductor diode is simply bringing these materials together constructed from the same base-Ge or Si? At the instant, the two materials have joined the electrons, and the hole in the region of the junction will semiconductor materials combine resulting in a lake of carriers in the region near the junction. 

This region of uncovered positive and negative ions is called the depletion region due to the depletion of carriers in this region.

Construction and type of P-N junction Diode

Types of semiconductor materials the most extensively used elements in the manufacture of junction diodes are germanium and silicon although some other materials are also assuming importance in recent years p-type semiconductors. 

A p-n junction diode known as a semiconductor and crystal diode consists of a P-N junction, formed either in germanium or silicon crystal. N-type semiconductor diode has two terminals namely anode and cathode. The anode refers to the P-type region and the cathode refers to the N-type region as shown in the figure below.

Fig. n and p-type

The arrowhead shown in the circuit symbol points to the direction of the current flow when it is forward-biased. It is the same direction in which the movement of holes takes place. The commercially available diodes, usually have some nations to identify the p and n terminals or leads.

 The standard notation consists of type numbers preceded by IN, such as IN 240 and IN 1250. Here 240 and 1250 correspond to color bands. In some diodes, the schematic symbol of a diode is painted or colors are marked on the body.

Fig.Diode p-n junction

The commercially available diodes, usually have some notations to identify the p and n terminals and lead. The standard notation consists of type numbers preceded by IN, such as IN 240 and IN 1250. Here 240 and 1250 correspond to color bands. In some diodes, the schematic symbol of a diode is painted or the color dots are marked on the body.

Potential Barrier and Biasing

A P-N junction diode which consists of P- and N-type semiconductors formed together to make a P-N junction is the place dividing the two zones known as a junction.

Potential barrier

As a result of diffusion, some electrons and holes migrate across the junction thereby forming a depletion layer on either side of the junction by neutralization of holes in the p-regional and of free electrons in the N- region. 

These diffusions of holes and electrons across the junction continue till a potential barrier is developed in the depletion layer which then prevents further diffusion. By the application of an external voltage, this potential barrier is either increased or decreased.

The barrier voltage of a P-N junction depends upon three factors namely density, electronic charge, and temperature. For a given P-N junction, the first two factors are constant, thus making the value of  Vb dependent only on temperature. 

It has been observed that for both germanium and silicon the value of Vb decrease by 2m Vl degrees celsius. Mathematically, the decrease in barrier voltage is -0.002* delta t, where delta t is the increase in temperature in degrees Celsius. 

Forward biasing

Fig. Forward biasing

The junction is said to be biased in the forward direction when the positive battery terminal is connected to the p-type region and the negative battery terminal to the n-type. This arrangement permits the flow of current across the P-N junction. 

The holes are repelled by the positive battery terminals and electrons by the negative battery terminal with the result that both holes and electrons will be driven towards the junction where they will recombine. 

Hence as long as the battery voltage is applied large current flows. In other words, the forward bias lowers the potential barrier across the depletion layer thereby allowing more current to flow across the junction.

Reverse biasing

Fig.Reverse biasing

The junction is said to be reversed biased also called Zener diode when battery connections to the battery are reversed holes are attracted by the negative battery terminal and electrons by the positive battery terminal so that both holes and electrons move away from the junction.

 Since there is no recombination of electron-hole pairs, the diode current is negligible and the junction has high resistance. Reverse biasing increases the potential barrier at the junction, thereby allowing very little current to flow through the junction.

V-I Characteristics of a P-N junction Diode

The V-I voltage-ampere characteristic of a typical p-n junction diode with respect to break-down voltage.

Fig.     V-I Characteristics of a P-N junction Diode
  • For typical junction concentration the current densities at a temperature of 300K, forward voltage ranges between 0.2 and 0.3 in germanium and between 0.5 and 0.75 volts in silicon.
  • The reverse current s related to minority carrier concentration, which depends upon temperature and the energy of the material.
  • Reverse current increases exponentially with temperature. It is a limiting factor in the high-temperature junction of semiconductor junction devices.
  • The high-frequency response of a semiconductor diode may be seriously limited by the charge stored in the depletion region. 
  • This charge gives a capacitive effect since it changes with voltage the value of the stored charge is that of the ionized impurity atoms in the depletion regions on either side of the junction.
  • The width of the depletion region increases with higher doping. The result is lower capacitance, as in the case of a parallel-plate capacitor with wider spacing between plates.
  • The maximum reverse voltage of a P-N junction is limited by the field in the depletion region. The field accelerates carriers, which may gain enough energy to create new hole-electron pairs by colliding with atoms of the lattice structure. 
  • Each of these carriers may also create a hole-electron pair. As reverse voltage is increased, an avalanche breakdown point is reached at which this multiplicative action causes the current to increase abruptly.
  • Avalanche breakdown voltage is higher in lightly doped regions, since the depletion region is wider, making the terminal electric field smaller for any given voltage.

Application of Semiconductor Devices

Semiconductor devices are electronic components that make use of the electrical properties of semiconductor materials, such as silicon and germanium, to control the flow of electrical current. These devices have a wide range of applications in various fields, including:

  1. Computing and electronics: Semiconductor devices are used in the production of computer processors, memory chips, and other electronic components.
  2. Communications: Semiconductor devices are used in the production of transistors, which are used in radio and television transmitters, mobile phones, and other communication devices.
  3. Power electronics: Semiconductor devices, such as diodes and transistors, are used in power supplies, inverters, and other power electronic devices.
  4. Automotive electronics: Semiconductor devices are used in the production of electronic control units (ECUs), which are used to control various systems in modern cars, such as engine management, anti-lock braking systems, and traction control.
  5. Industrial automation: Semiconductor devices, such as transistors and integrated circuits, are used in the production of programmable logic controllers (PLCs), which are used to control industrial processes.
  6. Medical equipment: Semiconductor devices are used in the production of diagnostic and therapeutic equipment, such as imaging systems and radiation therapy devices.
  7. Solar energy: Semiconductor devices, such as photovoltaic cells, are used to convert solar energy into electrical energy.
  8. LED: Light Emitting diodes (LEDs) are semiconductor devices that emit light when a current is applied to them, they are widely used in lighting, signaling, and display applications.

These are just a few examples of the many ways in which semiconductor devices are used in various fields. Their application is vast and still growing as the technology advancements.

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