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Zener effect 1

Zener effect

The I-V curve for a diode showing avalanche and Zener breakdown. Note that the

voltage increments in the negative range of the x-axis are larger than those in the

positive range

The Zener effect is a type of electrical

breakdown in a reverse biased p-n diode

in which the electric field across the

diode breaks some of the covalent

bonds of the semiconductor atoms

leading to a large number of free

minority carriers, which suddenly

increase the reverse current. [1] Zener

breakdown is employed in a Zener

diode.

Mechanism

Under a very high reverse voltage, the

p-n junction's depletion region expands

leading to a high strength electric field

across the junction. This electric field

acts to break covalent bonds of the

semiconductor atoms which liberates a

large number of free minority carriers.

This suddenly increases the reverse current and give rise to the high slope resistance of the Zener diode (i.e. the

voltage across the diode stays very close to a well defined and constant value, with increasing current).

Relationship to the avalanche effectThe Zener effect is distinct from avalanche breakdown which involves minority carrier electrons in the transition

region which are accelerated by the electric field to energies sufficient to free electron-hole pairs via collisions with

bound electrons. Either the Zener or the avalanche effect may occur independently, or both may occur

simultaneously. In general, diode junctions which break down below 5 V are caused by the Zener effect, while

junctions which experience breakdown above 5 V are caused by the avalanche effect. Intermediate breakdown

voltages (around 5V) are usually caused by a combination of the two effects. This Zener breakdown voltage is found

to occur at electric field intensity of about 3 10 7 V/m. [1] Zener breakdown occurs in heavily doped junctions

(p-type semiconductor moderately doped and n-type heavily doped), which produces a narrow depletion region. [2]

The avalanche breakdown occurs in lightly doped junction, which produces a wider depletion layer. Temperature

increases in the junction decrease Zener breakdown and increase the contribution of avalanche breakdown.

References[1] "PN junction breakdown characteristics" (http:/ / www. circuitstoday. com/ pn-junction-breakdown-characteristics). Circuits Today. August

25 2009. . Retrieved August 16 2011.

[2] (http:/ / people. seas. harvard. edu/ ~jones/ es154/ lectures/ lecture_2/ breakdown/ breakdown. html) Zener and Avalanche

Breakdown/Diodes, School of Engineering and Applied Sciences, Harvard University

http://people.seas.harvard.edu/~jones/es154/lectures/lecture_2/breakdown/breakdown.htmlhttp://www.circuitstoday.com/pn-junction-breakdown-characteristicshttp://en.wikipedia.org/w/index.php?title=Electronhttp://en.wikipedia.org/w/index.php?title=Avalanche_breakdownhttp://en.wikipedia.org/w/index.php?title=Depletion_regionhttp://en.wikipedia.org/w/index.php?title=Zener_diodehttp://en.wikipedia.org/w/index.php?title=Zener_diodehttp://en.wikipedia.org/w/index.php?title=Electric_currenthttp://en.wikipedia.org/w/index.php?title=Charge_carriers_in_semiconductorshttp://en.wikipedia.org/w/index.php?title=Atomhttp://en.wikipedia.org/w/index.php?title=Semiconductorhttp://en.wikipedia.org/w/index.php?title=Covalent_bondhttp://en.wikipedia.org/w/index.php?title=Covalent_bondhttp://en.wikipedia.org/w/index.php?title=Electric_fieldhttp://en.wikipedia.org/w/index.php?title=P-n_diodehttp://en.wikipedia.org/w/index.php?title=P-n_junction%23Reverse_biashttp://en.wikipedia.org/w/index.php?title=File%3AI-V_curve_for_a_Zener_Diode.svghttp://en.wikipedia.org/w/index.php?title=Current%E2%80%93voltage_characteristic

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Article Sources and Contributors 2

Article Sources and ContributorsZener effect Source : http://en.wikipedia.org/w/index.php?oldid=514831684 Contributors : Cyan.aqua, Larryisgood, LittleWink, MarkusHagenlocher, Not your siblings' deletionist, Rchandra,Wbm1058, 2 anonymous edits

Image Sources, Licenses and ContributorsFile:I-V curve for a Zener Diode.svg Source : http://en.wikipedia.org/w/index.php?title=File:I-V_curve_for_a_Zener_Diode.svg License : Creative Commons Attribution-Sharealike 3.0 Contributors : User:Fred the Oyster

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