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The Malorlty The Minority P-Type: The Holes Are Carrieis, While Electrons Are Carriers in

This document discusses p-type doping of semiconductors. P-type doping creates an abundance of holes by substituting trivalent atoms like boron into the silicon crystal lattice. This results in an electron being missing from one of the possible covalent bonds of the atom. The atom can then accept an electron from the valence band to complete its fourth bond, leaving behind a hole. When a sufficient number of these acceptor atoms are added, the number of holes greatly outnumbers the excited electrons, making holes the majority carriers and electrons the minority carriers in p-type materials.

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Nayan Mridha
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60 views1 page

The Malorlty The Minority P-Type: The Holes Are Carrieis, While Electrons Are Carriers in

This document discusses p-type doping of semiconductors. P-type doping creates an abundance of holes by substituting trivalent atoms like boron into the silicon crystal lattice. This results in an electron being missing from one of the possible covalent bonds of the atom. The atom can then accept an electron from the valence band to complete its fourth bond, leaving behind a hole. When a sufficient number of these acceptor atoms are added, the number of holes greatly outnumbers the excited electrons, making holes the majority carriers and electrons the minority carriers in p-type materials.

Uploaded by

Nayan Mridha
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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formation in sucha materialfar exceeds

of a hole.thenumberof electrons thenumberof


are the majoritycarriersandthe holesare the minority
In thiscasethe electrons
holes.
Becausethe tive-electronatomshavean extraelectronto "donate".
carriers. - they are
donoratoms.
called
Thepurpose
(luping:
Ptype 0f p-type istocreate
dGPing of holes.
anabundance In the
caseofsilicona trivalentatom. suchas boron. is substituted
into the crystallattice.The
resulliSthatan electronis missingfrom oneofthe four possiblecovalentbonds.Thusthe
atomcanacceptanelectron from thevalence
bandtocompletethefourthbond.resulting
of a hole.Suchdopants
intheforthatlon Whena sufficiently
arecalledacceptors. large
number0i acceptorsare added the holes greatly outnumberthe excited electrons.Thus.
the arethemalorlty while
carrieis, aretheminority
electrons inp-type
carriers
holes
materIa s

3 16-Explainphysically asa rectiner.


howa p-njunctionfunctions
[Model Question]
Answer:
Whena P-N junction diode is forward-biasedand the applied voltage is increasedfrom
zero.hardly any current flows through the device in the beginning. It is so becausethe
externalvoltage is being opposed by the internal barrier voltage VB whose value is 0.7 V
for Silicon and 0.3 V for Ge. As soon as VB is neutralized, current through the diode
increasesrapidly with increasing applied battery voltage. So, in forward bias condition,
the P-N junction diode behaves like a closed switch. When a P-N junction diode is
reversebiased, majority carriers are blocked and only a small. current (due to minority
carriers)flows through the diode. It is of the order of nanoamperes (nA) for Si and
microamperes(ttA) for Ge. For all practical purposes,this current is almost negligible.
So.in Reversebias condition..the P-N junction diode behaveslike an open switch. So.
theabovediscussionshows that the P-N junction functions as a rectifier.

3 17.Write short noteson the following:


a) Forward Voltage drop
b) Peak inverse Voltage
c) Maximum forward current
d) Leakage current
e) Junction Capacitance. [Model Question]
Answer:
2) Forward voltage drop (Vf)
Anyelectronicsdevice passingcurrent will develop a resultingvoltage acrossit and this
diodecharacteristicIS of great importance, especially for power rectitIcation where power
will be higher for a high forward voltage dr0p. Also RF diodes often need a small
losses
forwardvoltagedrop as signalsmay be small but still needto overcome it.
Thevoltageacrossa PN junctiondiodearisesfor two reasons.The first of the natureof
PN junctionand resultsfrom the turn-onvoltagementionedabove.t
semiconductor
the.
ThIsvoltageenablesthe depletionlayer to be overcomeand for currentto flow. The
Secondarises from the nonnal resistive losses in the device. As a result a figure for the

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