7/30/2019 Zener Effect
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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_characteristic7/30/2019 Zener Effect
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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
LicenseCreative Commons Attribution-Share Alike 3.0 Unported
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