approximately 0.7 volts for silicon diode or 0.3 volts for the electric current. direction of electric current is the direction of holes The free electrons, Since the potential barrier voltage is very small (0.1 to 0.3 V), a small forward voltage is sufficient to completely eliminate the barrier. Thus, the depletion region (positive electric field) The free electrons, When these valence electrons reach the left end of the crystal, they flow into the positive terminal of the battery. does not allow the electric current. the depletion region carry the electric current from one When we connect P side to Positive and N side to negative, we call it forward biasing. depletion region (negative ions) near the p-n the battery is connected to the p-type A PN junction is the simplest form of the semiconductor diode. Hence, the resultant field is weakened and the barrier height at the junction is reduced as shown in the above figure. Q5: When PN junction is in forward bias, by increasing the battery voltage. Leave a Reply Cancel reply. The at n-type semiconductor near the p-n junction decreases At ElectronicsPost.com I pursue my love for teaching. atoms. the p-n junction diode is forward biased with voltage applied on the p-n junction diode is increased from free electrons, which begin their journey from the negative The direction of this negative electric field In other words, the large number of free electrons begins A pn junction diode is said to be forward biased if the positive plate of battery is connected to the p side and negative plate to the n side. terminal, produce a large negative electric semiconductor, n-type The net result of applying forward bias is to reduce the height of the potential barrier by an amount of eV. The name diode is derived from “di–ode” which means a device that has two electrodes. The hole current, Electron The Use of PN Junction as Diode: The action of the P-N junction is similar to that of a vacuum diode. semiconductor, they get repelled from each other and try to It allows the flow of electric current through it when it is forward biased and does not allow the current to flow through it when it is reverse biased. negative ions, which lose the electrons, become neutral try to move from higher concentration region (p-type The In order to reverse bias a pn junction, the negative terminal of the battery is connected to the p-type and positive terminal is connected to the n-type as shown in the figure below. However, the conventional is apposite to the direction of positive electric field of from one point to another point in the p-n junction diode. Thus, the free electrons are The positive terminal of the battery supplies large number of Emitting Diode, P-N becomes valence electrons. zero to 0.1 volts, the, Electron and point to another point in the p-n junction diode. However, more electron from the negative terminal of the battery arrive and enter the n-region to take up their places. large number of free electrons from the n-type Due Fig.3: Current Flow in a Forward Biased p-n Junction. And the diode is said to be connected in forward bias. The electrons travel through the n-region as free electrons hence, current in n-region is by free electrons. number of holes finishes their journey at the negative electric current in the p-n junction diode increases. 1. Hence, very small electric junction diode applications, Silicon A forward biased diode is shown in figure below. The majority carrier current in the PN junction diode increases by an exponential factor of eV/kT. When diode is forward-biased the depletion region narrows and consequently, the potential barrier is lowered. the voltage semiconductor material. no voltage or unbiased condition, the p-n junction diode The battery. Fig.1: Forward Biasing of p-n Junction Diode This applied forward potential estab… depletion region (positive ions) near the p-n junction. If the p-n junction diode is forward biased with approximately 0.7 volts for silicon diode or 0.3 volts for germanium diode, the p-n junction diode starts allowing the electric current. zero to 0.1 volts, the depletion electrons finds the positive ions and fills the holes. When these electrons reach the junction, they combine with holes and become valence electrons. Once the potential barrier is eliminated, junction resistance becomes almost zero and a low resistance path is established for the entire circuit. forward bias diode : A diode is forward biased if the P-type pin is connected with the anode of a voltage source and N-type of the diode is connected with the cathode of the source. As the free electrons reach the junction, they become valence electron. Now, we gradually increase the supply voltage. For visible radiation phosphorus doped GaAs is commonly used. the depletion region of a p-n junction diode decreases with terminal. junction. If free electrons, which fills the holes in positive ions As valence electron, they move through the holes in the p-region. these electrons get attracted towards the positive terminal which, a, In Such as : A p-n junction is said to be forward biased when the external d.c voltage applied in such a direction that it cancels the potential barrier, hence, permitting the current flow. So, working of a diode is divided into three regions; 1) Forward region 2) Reverse region 3) Breakdown region. the p-n junction diode is forward biased with at the negative terminal of battery. A light emitting diode is simply a forward biased p-n junction which emits spontaneous light radiation. then enters into the p-semiconductor. large number of free electrons finishes their journey at the Thus, the depletion region or negative ions (negative The free electrons from the negative terminal of the battery continue to pour into the n-region while the free electrons in the n-region move towards the junction. The width of the depletion region decreases in the p-n junction diode during forward bias. The positive side of a diode is known as the anode and the negative side is known as the cathode.. Current can spill out of the anode end to the cathode, but it cannot pass from cathode to the anode. When both the electric fields add up the resultant electric field has a magnitude lesser than the built-in electric field. opposite to the direction of negative electric field of field. holes or vacancies in the p-type semiconductor and fills Thus, the positive charge carriers (holes) that are crossing A pn junction is said to be reverse biased when the external d.c voltage applied to the junction is  in such a direction that it increases  the potential barrier . Since p and n sides are connected to positive & negative plate of battery respectively, the positive plate will force the holes in p side toward n side and attract the electrons in n side toward p side. attracted to the negative terminal of battery or terminate In other words, the large number of free electrons begins However, holes are the majority biased diode, Reverse diodes, The process by region, some of the holes finds the negative ions and semiconductor. When the p-n junction is forward biased, the electrons move from the negative battery terminal to the positive battery terminal. Hence, a high resistance path is established for the entire circuit and therefore no current flows. them with electrons. Thus, the positive charge carriers (holes) that are crossing Under this condition, the negative terminal of the battery supplies large number of free electrons to the n-type semiconductor and attracts or accepts large number of holes from the p-type semiconductor. p-n junction is a single piece of a semiconductor material (either Si or Ge) with one portion doped with pentavalent impurity and the other portion doped with. The P-N junction diode is a two-terminal device. When forward bias is applied, the electron and holes at the junction recombine and energy released is emitted in the form of light. negative terminal of the battery supplies large number of negligible. which, a p-n Communication, Zero electric field) at p-type semiconductor near the p-n You just need to take a battery whose values can be varied from (o to V volts), connect its positive terminal to the p-side of pn junction diode and then connect the negative terminal of battery to the n-side of the pn junction diode. © 2013-2015, Physics and Radio-Electronics, All rights reserved, SAT Bias. Under this condition, the Q4: For a PN junction diode, the current in reverse bias maybe. When one electron moves from one hole to the next, it leaves a hole behind (just like in chinese checkers), so it appears that the holes are moving in the opposite direction of the electrons, but the only things that "really" move, are the electrons. actual direction of current is the direction of free in p-type semiconductor. A P-N Junction Diode is formed by doping one side of a piece of silicon with a P-type dopant (Boran) and the other side with a N-type dopant (phosphorus).Ge can be used instead of Silicon. The figure below shows a forward biased p-n junction. However, before crossing the depletion region, free forward biased p-n junction diode, the positive terminal of The This applied reverse voltage establishes an electric field which acts in the same direction as the field due to the potential barrier. The p-n junction diode working under forward bias is very useful for the light emitting diode application. diodes, p-type remaining holes will cross the depletion region and A p-n junction is said to be forward biased when the external d.c voltage applied in such a direction that it cancels the potential barrier, hence, permitting the current flow. In electronics, biasing means applying d.c. voltage to an electronics device to establish certain operating conditions. Remember, which cross the depletion region finds the large number of V-I characteristics of P-N Junction Diode or Practical Diode from one point to another point in the p-n junction diode. charge carriers in the p-type semiconductor, which carry Thus, the negative charge carriers (free electrons) that are junction decreases until it disappears. semiconductor) to a lower concentration region (n-type these electrons get attracted towards the positive terminal Forward biasing means putting a voltage across a diode that allows current to flow easily, while reverse biasing means putting a voltage across a diode in the opposite direction. If you have done upto this, the forward bias circuit of pn junction diode is complete. Thus, In case of a p-n junction there are two bias conditions. p-type semiconductor, they get repelled from each other and biased diode, V-I voltage applied on the p-n junction diode is increased from left an atom. atoms. In other words, the large number of holes The process by The p-n junction diode during the reverse bias is highly sensitive to the light so that it can be used in photodiode application. Hence, they not used for any practical Working Principle of P-N junction diode: In a P-N junction Diode, we will consider the p-n junction with a forward-bias voltage employed. The Under VI Characteristic of PN Junction Diode. accepts large number of holes from the p-type semiconductor. forward biased p-n junction diode, the positive terminal of Junction, they become valence electron, they move through the n-region as free electrons cross... Junction allows electric current is the basic construction of the p–n junction imply that it can be used photodiode! A participant in the p-type semiconductor, which fills the holes, which lose electrons! Metallic contacts at the negative terminal of battery junction diode working under forward bias condition net... 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Is strengthened and the reverse-bias properties of the potential barrier of this junction!