JoinedJun 8, 2005 Messages101 aided 10 Reputation20Reaction score7Trophy points1,298LocationPakistanActivity points2,080
built in potentialThe constructed in potential ( or obstacle potential ) for pn junctions is provided by complying with relation,Vbi = Vt ln(Na*Nd/ni²) i beg your pardon is usually of the order of 0.6V come 0.8 V. It deserve to be checked out that Vbi is purely duty of Temperature and Doping and also independent that the outside biasIncase of forward biased Pn junction, the obstacle is diminished to obstacle = Vbi-Vf --------- Eq (1)where Vf is the used forward prejudice potential. What wake up if Vf > Vbi? from Equation (1) => Vbi-Vf How have the right to we justification a an adverse barrier across the pn junction?
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JoinedOct 12, 2005 Messages46 aided 7 Reputation14Reaction score3Trophy points1,288LocationGreeceActivity points1,563
built-in potential
The obstacle is no negative.It"s just that the junction is front biased. The obstacle IS the integrated potential (I think). That"s why at around 0.7V (0.6-0.8V as you said) the obstacle is around to be overcome (or has been overcome) and the junction have the right to support large quantities of present while preserving an almost consistent voltage drop throughout it.

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JoinedJan 9, 2008 Messages207 helped 25 Reputation50Reaction score2Trophy points1,298LocationBangalore,IndiaActivity points2,657
built in potential equation
A forward voltage more than the call potential makes the barrier totally disappear. This will average the junction does no restrict the diffusng fee carriers throughout the junction and therefore the junction forwardly breaks down. The maker behaves as a resistive bar with really low resistivity, therefore huge forward present flows and it loss the diode. The an unfavorable contact potential simulates the condition of an ohmic contact where the jnction does not deplete the region of physics contact between the metal and the semiconductor and also therefore the resistivity that the semiconductor material offers rise come ohmic drop.
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JoinedJun 8, 2005 Messages101 aided 10 Reputation20Reaction score7Trophy points1,298LocationPakistanActivity points2,080
The an unfavorable contact potential simulates the problem of an ohmic call where the jnction walk not diminish the region of physics contact between the metal and the semiconductor and therefore the resistivity that the semiconductor material offers rise come ohmic drop.
1. Have the right to you elaborate above statement? 2. What around validity that the equation the evaluates the potential appearing across the pn junction (i.e. Potental throughout pn-junction = Vbi-Vf) i m sorry theoretically leader to an adverse potential across the junction incase of Vf>Vbi (which isn"t offcourse feasible because integrated field will constantly be command from n to p region of diode)Regards
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JoinedFeb 28, 2007 Messages152 aided 2 Reputation4Reaction score1Trophy points1,298Activity points2,377
diode developed in potential
The barrier potential(bp) is because of presence of positively doped and also negatively doped an ar side by side. Bp have the right to be considered as the resistance offered by the junction to the flow of electrons together intended by Vf. And also as lengthy as the bp hasnt to be broken, the electrons feel a greater pressure in the direction the bp.as soon as the Vf above bp(as in ur case), a big current flows.also, in electronics, over there is nothing any type of thing like an adverse current or voltage. Its simply the the contrary direction wrt come the reference direction.

See more: Amps To Coulombs Per Second Calculator, Coulombs Per Second To Amperes


JoinedJan 9, 2008 Messages207 assisted 25 Reputation50Reaction score2Trophy points1,298LocationBangalore,IndiaActivity points2,657
built in potential pn junction
When Vf over Vc the call potential, it means all the an are charges that were current at the depletion an ar to resist the diffusion of the bulk carriers space swept away and also there is no depletion an ar for the bulk carriers. The cathode and/or the anode space usually greatly doped so that at this problem the resistivity available by the device is very little leading come excessive present which heats up the an equipment and ultimately burns it. The forward failure voltage deserve to be boosted by making one of the electrode much less doped.In instance of ohmic contacts, if girlfriend remember, there are two varieties of straightforward metal semiconductor contact diodes, which gives rise come no depletion an ar depending on the work role of the semiconductor and also the metal and the doping type of the semiconductor. In these cases the junction an ar is rushed with the an are charges which actually helps diffusion by including drift to the bulk carriers unequal the instance of p-n junction diode whereby drift occurs because that the minority carriers. Thus there is no unilateral characteristics of the metal- semiconductor junction and depending ~ above the resistivity the the semiconductor existing flows in both direction as a linear role of voltage.