Lecture 2: Types of Semiconductors.pdf

Shri Shivaji Science College, Amravati (MS)
Shri Shivaji Science College, Amravati (MS)Assistant Professor em Shri Shivaji Science College, Amravati (MS)
Solid State Devices-I
Dr. Vaishali V. Deshmukh
Dept. of Physics
Shri Shivaji Science College, Amravati
Types of Semiconductor
Lecture -2
Silicon and Germanium
Commonly used Semiconductors
01
At absolute zero and Above absolute zero
Effect of temperature on Semiconductor
03
Current conduction due to holes
Concept of Hole current
04
Outline
Silicon and Germanium
Energy Bands in Semiconductors
02
Intrinsic and Extrinsic
Types of semiconductors
05
Commonly used semiconductors
Silicon
Germanium
Energy Bands in Silicon and Germanium
Band
Energy
(eV)
Band
Energy
(eV)
Silicon Germanium
1st Band
1st Band
Conduction
Band
Valence
Band
3rd Band
2nd Band
2nd Band
Valence
Band
Conduction
Band
1.1 eV
0.7 eV
Semiconductor is a substance
which has almost filled
valence band and nearly
empty conduction band with
a very small energy gap
(~1eV) separating the two.
Therefore, relatively small
energy is needed by their
valence electrons to cross
over to the conduction band.
Effect of temperature on semiconductor
At absolute zero
All the electrons are tightly
held by the semiconductor
atoms. Covalent bonds are very
strong and there are no free
electrons. Therefore
semiconductor behaves as a
perfect insulator.
Above absolute zero
Covalent bonds break due to
thermal energy supplied. Free
electrons exist in semiconductor
constitute electric current.
eV
Valence band
Conduction band
Hole Current
Types of Semiconductor
Fig: Classification of Semiconductors Fig: Intrinsic Semiconductor
 A semiconductor in an extremely pure form is known as intrinsic semiconductors.
 A semiconductor formed by adding suitable impurity to a pure semiconductor is k’as extrinsic semiconductor.
 Holes being positively charged move towards the negative terminal of supply. As the holes reach the negative terminal B, electron enters the
semiconductor crystal near the terminal and combine with holes, thus cancelling them. At the same time loosely held electrons near the positive
terminal A are attracted away from their atoms into the positive terminal. This creates few holes which again drift towards –ve terminal.
Extrinsic Semiconductor : n-type
Fig: Covalent bond in n-type Fig: Energy bands in n-type Fig: Current conduction in n-type
When a small amount of pentavalent impurity is added to a pure semiconductor, it is k’as n-type semiconductor. Fifth valence electron
of arsenic atom finds no place in covalent bond and is thus free. Many new free electrons are produced by the addition of pentavalent
impurity. Thermal energy of room temp still generates a few hole-electron pairs.However, the no. of free electrons provided by
pentavalent impurity far exceeds the holes. It is due to predominance of electrons over holes that is is called n-type semiconductor.
Extrinsic Semiconductor : p-type
Fig: Covalent bond in p-type Fig: Energy bands in p-type Fig: Current conduction in n-type
When a small amount of trivalent impurity is added to a pure semiconductor, it is called p-type semiconductor. Fourth bond is
incomplete; being short of one electron. This missing electron is called hole.The addition of trivalent impurity has produced large no. of
holes. However, there are few conduction band electrons due to thermal energy associated with room temp. But the holes far outnumber
the conduction band electrons. It is due to the predominance of holes over free electrons that it is called p-type semiconductor.
Charge on n-type & p-type semiconductor
The terms n- and p-type doped do only refer to the majority charge carriers. Each positive or negative charge carrier belongs to a
fixed negative or positive charged dopant. p and n type materials are NOT positively and negatively charged. An n-type material by
itself has mainly negative charge carriers (electrons) which are able to move freely, but it is still neutral because the fixed donor
atoms, having donated electrons, are positive. Similarly p-type material by itself has mainly positive charge carrier (holes) which
are able to move relatively freely, but it is still neutral because the fixed acceptor atoms, having accepted electrons, are negative.
In a tetravalent semiconductors like Si/Ge , if pentavalent materials like As are added then we get n-type semiconductor. In this n-type
semiconductor, four electrons of pentavalent element forms bond with the host element. Hence the excess one electron of dopant remains
very weakly bound to the atom of host material. As a result ionisation energy required to free this electron is very small. This required
ionisation energy is about 0.01 eV for Ge and about 0.05 eV for Si. Once required ionisation energy is supplied, the electron is free to move
and the dopant atom is positively charged. Similarly in p-type, when dopant receives electon from neighbouring Si/Ge atom, it becomes
negatively charged and create a positive hole in neighbouring Si/Ge atom. Thus free charged carriers i.e., electron and holes are created for
conduction in impurity semiconductors.But the crystal maintains an overall charge neutrality as the charge of additional charge carriers is just
equal in magnitude and opposite in sign to that of the ionised cores in the lattice.
(Donar ions)
(Acceptor ions)
Majority and Minority carriers
Difference between n-type & p-type
1
P-type semiconductor is formed due to the dopping of III group elements i.e. Boron, Aluminium, Thallium.
N-type semi conductor is formed due to dopping of V group elements Nitrogen, Phosporus, Arsenic, Antimony,
Bismoth.
2
In P-type impurity added creates vacancy of electrons (holes) called as Acceptor Atom.
In N-type impurity added provides extra electrons and is known as Donor Atom.
3
P-type are also known as Trivalent semi conductors.
N-type are also known pentavalent semiconductor.
4
P-type semiconductors is positive type semiconductor it means it deficiency of 1 electron is required.
N-type semiconductor is negative type semi-conductor it means excess of 1 electron is required.
5
In P-type semiconductor majority charge carries are holes and minority charge carries are electrons.
In N-type semiconductor majority charge carries are electrons and minority charge carries are hole.
6
A hole indicates a missing electron. In P-type no. of holes is more than the no. of electrons.
In N-type semiconductor the no. of holes is less than the no. of free electron.
Once we
accept our
limits, we go
beyond
them. Albert Einstein
THANK YOU
1 de 14

Recomendados

Module No. 25 por
Module No. 25Module No. 25
Module No. 25Rajput Abdul Waheed Bhatti
61 visualizações24 slides
Semiconductor.pptx por
Semiconductor.pptxSemiconductor.pptx
Semiconductor.pptxAnsumwiBoro2
12 visualizações13 slides
Session 3 por
Session 3Session 3
Session 3SIVALAKSHMIPANNEERSE
24 visualizações11 slides
Electronic por
ElectronicElectronic
ElectronicHarisKhan918416
16 visualizações28 slides
Semiconductor.pdf por
Semiconductor.pdfSemiconductor.pdf
Semiconductor.pdfKALPESH-JNV
112 visualizações13 slides
physics project class 12.docx por
physics project class 12.docxphysics project class 12.docx
physics project class 12.docxDeepakSaini59
381 visualizações15 slides

Mais conteúdo relacionado

Similar a Lecture 2: Types of Semiconductors.pdf

Class 12th Solids and semiconductor devices part 1 por
Class 12th Solids and semiconductor devices part 1Class 12th Solids and semiconductor devices part 1
Class 12th Solids and semiconductor devices part 1Arpit Meena
319 visualizações18 slides
semiconductor por
semiconductorsemiconductor
semiconductorAnshu Hilsa
456 visualizações21 slides
Semiconductor physics por
Semiconductor physicsSemiconductor physics
Semiconductor physicssangitaholkar
1.4K visualizações80 slides
Topic1_TypesofsemiconductorsandPNjunctionpptx__2023_02_21_08_57_13 (1).pptx por
Topic1_TypesofsemiconductorsandPNjunctionpptx__2023_02_21_08_57_13 (1).pptxTopic1_TypesofsemiconductorsandPNjunctionpptx__2023_02_21_08_57_13 (1).pptx
Topic1_TypesofsemiconductorsandPNjunctionpptx__2023_02_21_08_57_13 (1).pptxLeeroyMugadza
5 visualizações52 slides
Solids & Semiconductor Devices por
Solids & Semiconductor DevicesSolids & Semiconductor Devices
Solids & Semiconductor DevicesCHETAN D. GANDATE
65 visualizações18 slides
Semiconductor Devices Class 12 Part-1 por
Semiconductor Devices Class 12 Part-1Semiconductor Devices Class 12 Part-1
Semiconductor Devices Class 12 Part-1Self-employed
43.2K visualizações18 slides

Similar a Lecture 2: Types of Semiconductors.pdf(20)

Class 12th Solids and semiconductor devices part 1 por Arpit Meena
Class 12th Solids and semiconductor devices part 1Class 12th Solids and semiconductor devices part 1
Class 12th Solids and semiconductor devices part 1
Arpit Meena319 visualizações
semiconductor por Anshu Hilsa
semiconductorsemiconductor
semiconductor
Anshu Hilsa456 visualizações
Semiconductor physics por sangitaholkar
Semiconductor physicsSemiconductor physics
Semiconductor physics
sangitaholkar1.4K visualizações
Topic1_TypesofsemiconductorsandPNjunctionpptx__2023_02_21_08_57_13 (1).pptx por LeeroyMugadza
Topic1_TypesofsemiconductorsandPNjunctionpptx__2023_02_21_08_57_13 (1).pptxTopic1_TypesofsemiconductorsandPNjunctionpptx__2023_02_21_08_57_13 (1).pptx
Topic1_TypesofsemiconductorsandPNjunctionpptx__2023_02_21_08_57_13 (1).pptx
LeeroyMugadza5 visualizações
Solids & Semiconductor Devices por CHETAN D. GANDATE
Solids & Semiconductor DevicesSolids & Semiconductor Devices
Solids & Semiconductor Devices
CHETAN D. GANDATE65 visualizações
Semiconductor Devices Class 12 Part-1 por Self-employed
Semiconductor Devices Class 12 Part-1Semiconductor Devices Class 12 Part-1
Semiconductor Devices Class 12 Part-1
Self-employed43.2K visualizações
Edc unit 1 por Mukund Gandrakota
Edc unit 1Edc unit 1
Edc unit 1
Mukund Gandrakota1.3K visualizações
Applied physics unit4- part1 por UmayalSundariAR
Applied physics unit4- part1Applied physics unit4- part1
Applied physics unit4- part1
UmayalSundariAR117 visualizações
7760402.ppt por MilkTea45
7760402.ppt7760402.ppt
7760402.ppt
MilkTea453 visualizações
solids_and_semiconductor_devices_1.ppt por mragarwal
solids_and_semiconductor_devices_1.pptsolids_and_semiconductor_devices_1.ppt
solids_and_semiconductor_devices_1.ppt
mragarwal16 visualizações
Presentation report for Intrinsic & Extrinsic , N-type & P-type and Forward& ... por Obaid ur Rehman
Presentation report for Intrinsic & Extrinsic , N-type & P-type and Forward& ...Presentation report for Intrinsic & Extrinsic , N-type & P-type and Forward& ...
Presentation report for Intrinsic & Extrinsic , N-type & P-type and Forward& ...
Obaid ur Rehman244 visualizações
semiconductor physics,unit 5 por Kumar
semiconductor physics,unit 5semiconductor physics,unit 5
semiconductor physics,unit 5
Kumar 32.4K visualizações
Lecture 01 por FarhanIshraq6
Lecture 01Lecture 01
Lecture 01
FarhanIshraq627 visualizações
INVESTIGATORY PROJECT ON SEMICONDUCTOR by shivam jhade por bhopal
INVESTIGATORY PROJECT ON SEMICONDUCTOR by shivam jhade INVESTIGATORY PROJECT ON SEMICONDUCTOR by shivam jhade
INVESTIGATORY PROJECT ON SEMICONDUCTOR by shivam jhade
bhopal21.8K visualizações
Basic Electronics by Er. Swapnil Kaware por Prof. Swapnil V. Kaware
Basic Electronics by Er. Swapnil KawareBasic Electronics by Er. Swapnil Kaware
Basic Electronics by Er. Swapnil Kaware
Prof. Swapnil V. Kaware978 visualizações
1.Introduction to Electronics.pptx por kpdemon
1.Introduction to Electronics.pptx1.Introduction to Electronics.pptx
1.Introduction to Electronics.pptx
kpdemon22 visualizações
MODULE 1 modified - CET (1).pptx por KerenElisheba
MODULE 1 modified - CET (1).pptxMODULE 1 modified - CET (1).pptx
MODULE 1 modified - CET (1).pptx
KerenElisheba24 visualizações
Semiconductors N. m.Aher por NandalalAher1
Semiconductors N. m.AherSemiconductors N. m.Aher
Semiconductors N. m.Aher
NandalalAher1322 visualizações
Semiconductors por bijoycp
SemiconductorsSemiconductors
Semiconductors
bijoycp639 visualizações
Analog Electronic ppt by Being topper on Semiconductors por Vipin Kumar
Analog Electronic ppt by Being topper on SemiconductorsAnalog Electronic ppt by Being topper on Semiconductors
Analog Electronic ppt by Being topper on Semiconductors
Vipin Kumar1.8K visualizações

Mais de Shri Shivaji Science College, Amravati (MS)

Electrochemical technique 1: Cyclic Voltammery por
Electrochemical technique 1: Cyclic VoltammeryElectrochemical technique 1: Cyclic Voltammery
Electrochemical technique 1: Cyclic VoltammeryShri Shivaji Science College, Amravati (MS)
7 visualizações20 slides
Lecture 3: Solid State Devices II.pdf por
Lecture 3: Solid State Devices II.pdfLecture 3: Solid State Devices II.pdf
Lecture 3: Solid State Devices II.pdfShri Shivaji Science College, Amravati (MS)
55 visualizações16 slides
Lecture 1: Solid State Devices II.pdf por
Lecture 1: Solid State Devices II.pdfLecture 1: Solid State Devices II.pdf
Lecture 1: Solid State Devices II.pdfShri Shivaji Science College, Amravati (MS)
5 visualizações12 slides
Lecture 2: Solid State Devices II.pdf por
Lecture 2:  Solid State Devices II.pdfLecture 2:  Solid State Devices II.pdf
Lecture 2: Solid State Devices II.pdfShri Shivaji Science College, Amravati (MS)
6 visualizações18 slides
Lecture 5: Semiconductor Diode.pdf por
Lecture 5: Semiconductor Diode.pdfLecture 5: Semiconductor Diode.pdf
Lecture 5: Semiconductor Diode.pdfShri Shivaji Science College, Amravati (MS)
20 visualizações14 slides
Lecture 4: PN-Junction.pdf por
Lecture 4: PN-Junction.pdfLecture 4: PN-Junction.pdf
Lecture 4: PN-Junction.pdfShri Shivaji Science College, Amravati (MS)
16 visualizações12 slides

Mais de Shri Shivaji Science College, Amravati (MS)(13)

Último

selection of preformed arch wires during the alignment stage of preadjusted o... por
selection of preformed arch wires during the alignment stage of preadjusted o...selection of preformed arch wires during the alignment stage of preadjusted o...
selection of preformed arch wires during the alignment stage of preadjusted o...MaherFouda1
7 visualizações100 slides
별헤는 사람들 2023년 12월호 전명원 교수 자료 por
별헤는 사람들 2023년 12월호 전명원 교수 자료별헤는 사람들 2023년 12월호 전명원 교수 자료
별헤는 사람들 2023년 12월호 전명원 교수 자료sciencepeople
68 visualizações30 slides
DEVELOPMENT OF FROG.pptx por
DEVELOPMENT OF FROG.pptxDEVELOPMENT OF FROG.pptx
DEVELOPMENT OF FROG.pptxsushant292556
11 visualizações21 slides
Structure of purines and pyrimidines - Jahnvi arora (11228108), mmdu ,mullana... por
Structure of purines and pyrimidines - Jahnvi arora (11228108), mmdu ,mullana...Structure of purines and pyrimidines - Jahnvi arora (11228108), mmdu ,mullana...
Structure of purines and pyrimidines - Jahnvi arora (11228108), mmdu ,mullana...jahnviarora989
7 visualizações12 slides
Small ruminant keepers’ knowledge, attitudes and practices towards peste des ... por
Small ruminant keepers’ knowledge, attitudes and practices towards peste des ...Small ruminant keepers’ knowledge, attitudes and practices towards peste des ...
Small ruminant keepers’ knowledge, attitudes and practices towards peste des ...ILRI
6 visualizações6 slides
Study on Drug Drug Interaction Through Prescription Analysis of Type II Diabe... por
Study on Drug Drug Interaction Through Prescription Analysis of Type II Diabe...Study on Drug Drug Interaction Through Prescription Analysis of Type II Diabe...
Study on Drug Drug Interaction Through Prescription Analysis of Type II Diabe...Anmol Vishnu Gupta
28 visualizações12 slides

Último(20)

selection of preformed arch wires during the alignment stage of preadjusted o... por MaherFouda1
selection of preformed arch wires during the alignment stage of preadjusted o...selection of preformed arch wires during the alignment stage of preadjusted o...
selection of preformed arch wires during the alignment stage of preadjusted o...
MaherFouda17 visualizações
별헤는 사람들 2023년 12월호 전명원 교수 자료 por sciencepeople
별헤는 사람들 2023년 12월호 전명원 교수 자료별헤는 사람들 2023년 12월호 전명원 교수 자료
별헤는 사람들 2023년 12월호 전명원 교수 자료
sciencepeople68 visualizações
DEVELOPMENT OF FROG.pptx por sushant292556
DEVELOPMENT OF FROG.pptxDEVELOPMENT OF FROG.pptx
DEVELOPMENT OF FROG.pptx
sushant29255611 visualizações
Structure of purines and pyrimidines - Jahnvi arora (11228108), mmdu ,mullana... por jahnviarora989
Structure of purines and pyrimidines - Jahnvi arora (11228108), mmdu ,mullana...Structure of purines and pyrimidines - Jahnvi arora (11228108), mmdu ,mullana...
Structure of purines and pyrimidines - Jahnvi arora (11228108), mmdu ,mullana...
jahnviarora9897 visualizações
Small ruminant keepers’ knowledge, attitudes and practices towards peste des ... por ILRI
Small ruminant keepers’ knowledge, attitudes and practices towards peste des ...Small ruminant keepers’ knowledge, attitudes and practices towards peste des ...
Small ruminant keepers’ knowledge, attitudes and practices towards peste des ...
ILRI6 visualizações
Study on Drug Drug Interaction Through Prescription Analysis of Type II Diabe... por Anmol Vishnu Gupta
Study on Drug Drug Interaction Through Prescription Analysis of Type II Diabe...Study on Drug Drug Interaction Through Prescription Analysis of Type II Diabe...
Study on Drug Drug Interaction Through Prescription Analysis of Type II Diabe...
Anmol Vishnu Gupta28 visualizações
ALGAL PRODUCTS.pptx por RASHMI M G
ALGAL PRODUCTS.pptxALGAL PRODUCTS.pptx
ALGAL PRODUCTS.pptx
RASHMI M G 7 visualizações
ELECTRON TRANSPORT CHAIN por DEEKSHA RANI
ELECTRON TRANSPORT CHAINELECTRON TRANSPORT CHAIN
ELECTRON TRANSPORT CHAIN
DEEKSHA RANI11 visualizações
Discovery of therapeutic agents targeting PKLR for NAFLD using drug repositio... por Trustlife
Discovery of therapeutic agents targeting PKLR for NAFLD using drug repositio...Discovery of therapeutic agents targeting PKLR for NAFLD using drug repositio...
Discovery of therapeutic agents targeting PKLR for NAFLD using drug repositio...
Trustlife146 visualizações
Effect of Integrated Nutrient Management on Growth and Yield of Solanaceous F... por SwagatBehera9
Effect of Integrated Nutrient Management on Growth and Yield of Solanaceous F...Effect of Integrated Nutrient Management on Growth and Yield of Solanaceous F...
Effect of Integrated Nutrient Management on Growth and Yield of Solanaceous F...
SwagatBehera95 visualizações
scopus cited journals.pdf por KSAravindSrivastava
scopus cited journals.pdfscopus cited journals.pdf
scopus cited journals.pdf
KSAravindSrivastava15 visualizações
ZEBRA FISH: as model organism.pptx por mahimachoudhary0807
ZEBRA FISH: as model organism.pptxZEBRA FISH: as model organism.pptx
ZEBRA FISH: as model organism.pptx
mahimachoudhary080711 visualizações
IMMUNODIAGNOSTICS KITS.pdf por vetrivel303632
IMMUNODIAGNOSTICS KITS.pdfIMMUNODIAGNOSTICS KITS.pdf
IMMUNODIAGNOSTICS KITS.pdf
vetrivel30363217 visualizações
Radioactive and Non- radioactive probes por Nathiya .T Nathiya.T
Radioactive and Non- radioactive probesRadioactive and Non- radioactive probes
Radioactive and Non- radioactive probes
Nathiya .T Nathiya.T6 visualizações
Note on the Riemann Hypothesis por vegafrank2
Note on the Riemann HypothesisNote on the Riemann Hypothesis
Note on the Riemann Hypothesis
vegafrank28 visualizações
Experimental animal Guinea pigs.pptx por Mansee Arya
Experimental animal Guinea pigs.pptxExperimental animal Guinea pigs.pptx
Experimental animal Guinea pigs.pptx
Mansee Arya40 visualizações
Factors affecting fluorescence and phosphorescence.pptx por SamarthGiri1
Factors affecting fluorescence and phosphorescence.pptxFactors affecting fluorescence and phosphorescence.pptx
Factors affecting fluorescence and phosphorescence.pptx
SamarthGiri17 visualizações

Lecture 2: Types of Semiconductors.pdf

  • 1. Solid State Devices-I Dr. Vaishali V. Deshmukh Dept. of Physics Shri Shivaji Science College, Amravati
  • 3. Silicon and Germanium Commonly used Semiconductors 01 At absolute zero and Above absolute zero Effect of temperature on Semiconductor 03 Current conduction due to holes Concept of Hole current 04 Outline Silicon and Germanium Energy Bands in Semiconductors 02 Intrinsic and Extrinsic Types of semiconductors 05
  • 5. Energy Bands in Silicon and Germanium Band Energy (eV) Band Energy (eV) Silicon Germanium 1st Band 1st Band Conduction Band Valence Band 3rd Band 2nd Band 2nd Band Valence Band Conduction Band 1.1 eV 0.7 eV Semiconductor is a substance which has almost filled valence band and nearly empty conduction band with a very small energy gap (~1eV) separating the two. Therefore, relatively small energy is needed by their valence electrons to cross over to the conduction band.
  • 6. Effect of temperature on semiconductor At absolute zero All the electrons are tightly held by the semiconductor atoms. Covalent bonds are very strong and there are no free electrons. Therefore semiconductor behaves as a perfect insulator. Above absolute zero Covalent bonds break due to thermal energy supplied. Free electrons exist in semiconductor constitute electric current. eV Valence band Conduction band Hole Current
  • 7. Types of Semiconductor Fig: Classification of Semiconductors Fig: Intrinsic Semiconductor  A semiconductor in an extremely pure form is known as intrinsic semiconductors.  A semiconductor formed by adding suitable impurity to a pure semiconductor is k’as extrinsic semiconductor.  Holes being positively charged move towards the negative terminal of supply. As the holes reach the negative terminal B, electron enters the semiconductor crystal near the terminal and combine with holes, thus cancelling them. At the same time loosely held electrons near the positive terminal A are attracted away from their atoms into the positive terminal. This creates few holes which again drift towards –ve terminal.
  • 8. Extrinsic Semiconductor : n-type Fig: Covalent bond in n-type Fig: Energy bands in n-type Fig: Current conduction in n-type When a small amount of pentavalent impurity is added to a pure semiconductor, it is k’as n-type semiconductor. Fifth valence electron of arsenic atom finds no place in covalent bond and is thus free. Many new free electrons are produced by the addition of pentavalent impurity. Thermal energy of room temp still generates a few hole-electron pairs.However, the no. of free electrons provided by pentavalent impurity far exceeds the holes. It is due to predominance of electrons over holes that is is called n-type semiconductor.
  • 9. Extrinsic Semiconductor : p-type Fig: Covalent bond in p-type Fig: Energy bands in p-type Fig: Current conduction in n-type When a small amount of trivalent impurity is added to a pure semiconductor, it is called p-type semiconductor. Fourth bond is incomplete; being short of one electron. This missing electron is called hole.The addition of trivalent impurity has produced large no. of holes. However, there are few conduction band electrons due to thermal energy associated with room temp. But the holes far outnumber the conduction band electrons. It is due to the predominance of holes over free electrons that it is called p-type semiconductor.
  • 10. Charge on n-type & p-type semiconductor The terms n- and p-type doped do only refer to the majority charge carriers. Each positive or negative charge carrier belongs to a fixed negative or positive charged dopant. p and n type materials are NOT positively and negatively charged. An n-type material by itself has mainly negative charge carriers (electrons) which are able to move freely, but it is still neutral because the fixed donor atoms, having donated electrons, are positive. Similarly p-type material by itself has mainly positive charge carrier (holes) which are able to move relatively freely, but it is still neutral because the fixed acceptor atoms, having accepted electrons, are negative. In a tetravalent semiconductors like Si/Ge , if pentavalent materials like As are added then we get n-type semiconductor. In this n-type semiconductor, four electrons of pentavalent element forms bond with the host element. Hence the excess one electron of dopant remains very weakly bound to the atom of host material. As a result ionisation energy required to free this electron is very small. This required ionisation energy is about 0.01 eV for Ge and about 0.05 eV for Si. Once required ionisation energy is supplied, the electron is free to move and the dopant atom is positively charged. Similarly in p-type, when dopant receives electon from neighbouring Si/Ge atom, it becomes negatively charged and create a positive hole in neighbouring Si/Ge atom. Thus free charged carriers i.e., electron and holes are created for conduction in impurity semiconductors.But the crystal maintains an overall charge neutrality as the charge of additional charge carriers is just equal in magnitude and opposite in sign to that of the ionised cores in the lattice. (Donar ions) (Acceptor ions)
  • 12. Difference between n-type & p-type 1 P-type semiconductor is formed due to the dopping of III group elements i.e. Boron, Aluminium, Thallium. N-type semi conductor is formed due to dopping of V group elements Nitrogen, Phosporus, Arsenic, Antimony, Bismoth. 2 In P-type impurity added creates vacancy of electrons (holes) called as Acceptor Atom. In N-type impurity added provides extra electrons and is known as Donor Atom. 3 P-type are also known as Trivalent semi conductors. N-type are also known pentavalent semiconductor. 4 P-type semiconductors is positive type semiconductor it means it deficiency of 1 electron is required. N-type semiconductor is negative type semi-conductor it means excess of 1 electron is required. 5 In P-type semiconductor majority charge carries are holes and minority charge carries are electrons. In N-type semiconductor majority charge carries are electrons and minority charge carries are hole. 6 A hole indicates a missing electron. In P-type no. of holes is more than the no. of electrons. In N-type semiconductor the no. of holes is less than the no. of free electron.
  • 13. Once we accept our limits, we go beyond them. Albert Einstein