The diode iii-vvvrelationship can be modeled with an equation. Ge at room temperature) when depletion region width is much smaller than diffusion length of minority carriers, and the device is much longer than the diffusion lengths. Unlike other types of semiconductor diodes, the shockley diode has more than a single PN junction. {\displaystyle R_{1}} {\displaystyle V_{J}} The Shockley ideal diode equation or diode law is derived from the assumption that only processes giving rise to current in the diode are drift (because of electrical field), diffusion, and thermal recombination-generation. This of course would require an infinite thickness to provide an infinite amount of recombination. The diode equation gives an expression for the current through a diode as a function of voltage. It conducts when it is forward biased and stops conducting when it is reverse biased. Now, how close is close and how far is far? is small, we obtain This decrease is due to an excess of recombination of electron-hole pairs over generation of electron-hole pairs. Derivation. Print. The reverse breakdown region is not modeled by the Shockley diode equation. Fundamentals of Electrical Engineering. Here I won't be deriving the original 1949 … Basically I have to dissect it. We then assume that most of the excess recombination (or decrease in hole current) takes place in a layer going by one hole diffusion length (Lp) into the n material and one electron diffusion length (Ln) into the p material, and that the difference between the quasi-Fermi levels is constant in this layer at VJ. In the case of large forward bias, a good approximation of the ideal diode equation is to simply set the second term of Equation \ref{eq1} to zero. Here is the way I … The small current that flows under high reverse bias is then the result of thermal generation of electron-hole pairs in the layer. The concentrations of electrons and holes in the layer is so small that recombination there is negligible. diff n drift jn =0 jn =−j The drift current is equal to the diffusion current for electrons in thermal equilibrium The drift current is equal to the diffusion current for holes in thermal equilibrium diff p drift jp =0 jp =−j with A having a value as high as 2 or 3. https://en.wikipedia.org/w/index.php?title=Shockley_diode_equation&oldid=988715494, Creative Commons Attribution-ShareAlike License, the difference between the quasi-Fermi level of the holes at the junction and that of the electrons at the junction. This page was last edited on 14 November 2020, at 21:00. 0, v \leq 0 \\ The Ideal Diode Law, expressed as: I = I 0 (e q V k T − 1) I minority carriers therefore diffuse towards the bulk giving rise to a diode current. Equation \ref{eq1} is also called the Shockley ideal diode equation or the diode law. Shockley derives an equation for the voltage across a p n junction in a long article published in 1949. 1 As for the second, the difference between the quasi-Fermi levels at the junction, he says that we can estimate the current flowing through the diode from this difference. It is equivalent to a thyristor with a disconnected gate. Simple Derivation Of Diode Equation Thread starter 03myersd; Start date Apr 16, 2009; Apr 16, 2009 #1 03myersd. exp Log(Concentration) Hole diffusion Electron diffusion n p(0) Minute increase p n(0) p no n po p po n no V Excess holes Excess electrons x x Neutral p-regionNeutral n SCL W As seen in the previous sections, a p-n junction diode creates the following current: under reverse bias, there is a small, constant reverse current, and under forward bias, there is a forward current that increases with voltage. 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