Introduction to pn junction the engineering projects. By exploring the electrical properties of silicon, it is possible to acquire an understanding of the inner workings of the pn junction. In this paper formation a pn junction diode is explained by vlsi fabrication steps which are stated below. The construction of led is similar to the normal pn junction diode except that gallium, phosphorus and arsenic materials are used for construction instead of silicon or germanium materials. The ptype semiconductor has excess holes and is of positive charge. Similarly, holes flow by diffusion from the ptype side to the ntype side.
Since the ntype region has a high electron concentration and the ptype a high hole concentration, electrons diffuse from the ntype side to the ptype side. In this video you will learn about the construction of a pn junction diode, working of it and the characteristics of it under forward and reverse. The word varicap is originated from the combination of word variable and capacitor. As shown in the figure, pn junction diode is a 2 terminal polarity sensitive device. Working principle of pn junction diode polytechnic hub.
A varactor diode is a pn junction diode that is especially operated in reverse biased mode. Pn junction diode baising and its vi characteristics elprocus. But in the case of photodiode the current can flow without application of reverse voltage, the pn junction of the photodiode is illuminated by light and light energy dislodge valence electrons and the diode starts conducting. Fabrication of pnjunction diode by ic fabrication process. A special type of pn junction diode that operates in reverse biased mode, more specifically in breakdown region is known as zener diode the doping level of the zener diode is somewhat higher than the normal pn junction diode.
The other differences between the pnjunction and zener diode are shown in the comparison. The pn junction is a junction formed together by ptype semiconductor and ntype semiconductor material. Note to those familiar with a diode turn on voltage. Pn junction diode construction working and uses electrical. A pn junction is the simplest form of the semiconductor diode. Diode is a basic element in electronic and digital circuit. In this tutorial, we will learn about pn junction diodes and in particular the characteristics and working of pn junction diode. Pn junctions are formed by joining ntype and ptype semiconductor materials, as shown below.
Before going to varactor diode, lets first take a look at the capacitor. This is the basic construction of the pn junction diode. The diode the diode is a two terminal semiconductor device that allows current to flow in only one direction. A pnjunction is formed when an ntype material is fused together with a ptype material creating a semiconductor diode. It is a device whose capacitance changes with the variation in the applied reverse bias potential. The pn junction is an interface between a ptype and an ntype region and is used to construct diodes and transistors.
Doping with acceptor creates p type semiconductor while doping with donors produces n type. Pn junction diode is one of the fundamental elements in electronics. If one side of a single crystal of pure semiconductor germanium ge or. It is constructed of a p and an n junction connected together. We have also learned about diffusion current, depletion region. You just need to take a battery whose values can be varied from o to v volts, connect its positive terminal to the pside of pn junction diode and then connect the negative terminal of battery to the nside of the pn junction diode. Figure 1the light emitting diode electrical symbol and practical structure diagram. Avalanche diode construction, working and its applications. In this type of diode, we dope one side of a semiconductor piece with an acceptor impurity and another side with a donor impurity. The pn junction is the fundamental building block of the electronic age. A light emitting diode led is essentially a pn junction diode. A pn junction diode is a two terminal single crystal semiconductor device whose one side is doped with acceptors and other side by donors.
The photodiode is made up of two layers of ptype and ntype semiconductor. Varactor diode is a pn junction diode whose capacitance is varied by varying the reverse voltage. Light emitting diode led working, construction and. When carriers are injected across a forwardbiased junction, it emits incoherent light. It is one of the simplest semiconductor devices as it allows current to flow in only one direction. Forward biasing a pn junction diode is very simple. Investigation of a barrier layer by the thermoprobe method pdf. Varactor diode definition, symbol, construction and. The point contact junction has very low value of the capacitance. A cert ain pn junction diode has a leakage current of 10. Definition, symbol, and types of diodes electrical4u. This page of application notes section covers pn junction diode applications.
Pn junction underbiasing 14 boltzmanns approximation. Pn junction is a significant building block and it is one among the indispensable structures. This is done to order to allow the light energy to pass through it. This is the voltage required to reach a flat band diagram and sets an upper limit typically an overestimate for the voltage that can be applied to a diode before it burns itself up. This understanding will lay a better foundation for exploring further into different aspects of semiconductor electronics. The behaviour of the pn junction with regards to the potential barriers width produces an asymmetrical conducting two terminal device, better known as the pn junction diode. The positive terminal of the battery is connected to the anode of a diode and negative terminal to the cathode when battery is not connected, there is a barrier potential of 0. In pn junction diode, potential barrier is approximately 0. The junction plays an important role in the development of the diode which is the building block of most of the semiconductor devices like transistors, bjts, solar cells and integrated circuits. Bjt bipolar junction transistor construction, types and.
Construction, working and characteristics of a pn junction diode. Najmabadi, ece65, winter 2012 high concentration of h on the p side holes diffuse towards the junction. A pn junction with open terminals excluding minority carriers f. Since a junction forms between a p type and n type material it is called as pn junction. Simplified physical structure construction on a cmos chip. The pn junction is formed by passing a large current about 200 ma for 1 to 100 millisecond duration. A diode is a tiny electronic component used in almost all the electronic circuits to enable the flow of current in only one direction. Now, if we join the two types of semiconductors ptype and ntype together then a new device is formed called as pn junction diode. Pn junction theory for semiconductor diodes electronicstutorials. These materials are ntype, having electrons are majority carrier and ptype material, having holes are majority carrier.
An avalanche diode is a one kind of diode that is designed to experience an avalanche breakdown at a particular reverse bias voltage. This diode emits laser light when it is forward biased. Most of the commercial leds are realized using a highly doped n and a p junction. A diode is formed by joining two equivalently doped ptype and ntype semiconductor. Pn junction diode baising and its vi characteristics. In a ptype semiconductor, the number p p of holes is much larger than the number of electrons n p p p n p. The diode is forwardbiased with a constantcurrent source of 1 ma at room temperature.
As only the junction is exposed to radiation, thus, the other portion of the glass material is painted black or is metallised. Silicon wafer cleaning rca process in the ic processing wafers it is necessary to maintain the purity and perfection of material. Semiconductor electronicsdiodeconstruction and operation. Principle, construction, working, characteristics, advantages, disadvantages and applications it is specifically fabricated pn junction diode. Photodetectors pn junction can detect light when reverse biased ptype ntype when the light illuminates the pn junction, the photons energy releases free electrons and holes. Working of pn junction diode with biasing, characteristics.
Pn junction diode is a device made of two semiconductor material joined together with the required amount of impurity. A pn junction diode is formed by doping one side of a piece of silicon with a ptype dopant boran and the other side with a ntype dopant phosphorus. The energy gap between the valence level and the conduction level is midway between that of insulators and conductors such as metals, and thermal energy causes. Junction coming to the equilibrium by balancing the fermi level ef ef the balance is achieved by electrons diffusing into a pside bringing an extra negative charge in there and by the holes diffusing into an nside bringing an extra negative charge in there pn. There are three biasing conditions for pn junction diode and this is based on the voltage applied. Construction and working of pn junction diode youtube. Pn junction lab free to use on allows simulation and study of a pn junction diode with different doping and materials. A pnjunction diode is formed when a ptype semiconductor is fused to an ntype semiconductor creating a potential barrier voltage across the diode junction. A pn junction is a boundary or interface between two types of semiconductor materials, ptype. In normal pn junction diodes, silicon is most widely used because it is less sensitive to the temperature. With proper biasing, pn diode allows current to flow in single direction. Holes are the majority carriers and electrons are the minority carriers. The boltzmann approximation is to say that the resulting current being small compared with the components of this current, we consider that we are still in quasi equilibrium and therefore that the currents equation is still valid by replacing v bi by v. When it is activated by applying the suitable voltages across its leads then it emits the light energy in the form of photons and the color of this light was determined by the band.
Learn about different types of diodes, their working, construction and applications. The pn junction of the device placed inside a glass material. This article discusses about a brief information about the construction and working of an avalanche diode. This pn diode applications are very useful for beginners. In ideal conditions, this pn junction behaves as a short circuit when it is forward biased, and as an open circuit when it is in the reverse biased. The word diode can be explained as di means two and ode is obtained from electrode. A pn junction diode is a twoterminal electronics element, which can be classified as either step graded or linear graded. The figure below shows the constructional detail of a photodiode. The diode conducts when forward bias is applied and it will introduce zero resistance in the circuit. Pn junction diode and characteristics of pn junction diode. They are referred to as photoelectrons and photoholes the applied voltage separates the photocarriers attracting electrons toward. Ripple factor, peak inverse voltage piv, capacitor input filter. Light emitting diode working, construction, types and. Diode as rectifier, half wave rectifier, full wave rectifier, bridge rectifier, output waveforms, definitions and derivations of idc, vdc, vrms, irms, efficiency.1398 1217 623 21 933 43 863 1429 98 784 685 469 843 388 1405 9 1097 1392 219 965 1317 1399 564 1280 940 420 992 281 1072 639 47 876 648 885 1292 618 437 752 119