2.PEL.1semikonduktor Jan04

04/11/23 1

NAMA PENSYARAH: NAMA PENSYARAH: TN. SYED ADNAN SYED TN. SYED ADNAN SYED

OTHMANOTHMAN

SEMICONDUCTOR SEMICONDUCTOR DEVICESDEVICES

EE201

2

CHAPTER 1

(N-type and P-type)

SEMICONDUCTORSEMICONDUCTOR

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Objectives:

1.1. Atomic structureAtomic structure

2.2. Insulators, conductors, Insulators, conductors, semiconductor.semiconductor.

3.3. Semiconductor characteristicSemiconductor characteristic

4.4. N-type and p-type N-type and p-type semiconductorsemiconductor

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Atomic StrukturAtomic Struktur

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Every atom consist of:Every atom consist of:i.i. ElectronElectron

-- smallest and lightest particlesmallest and lightest particle-- negative chargenegative charge-- move in high speed around move in high speed around nukleusnukleus

ii.ii. Proton Proton

-- 1800 times bigger than electron 1800 times bigger than electron

-- positive chargepositive charge

iii.iii. Neutron Neutron Same size of protonSame size of proton No chargeNo charge

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Atomic StructureAtomic Structure

Nukleus Electron orbit

++ +

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HidrogenHidrogen

+proton

electron

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Nukleus atom:-Nukleus atom:- carbon – 6 proton and 6 neutroncarbon – 6 proton and 6 neutron

cuprum – 29 proton, 29 neutroncuprum – 29 proton, 29 neutron

Aluminium – 13 proton, 13 neutronAluminium – 13 proton, 13 neutron

Silicon – 14 proton, 14 neutronSilicon – 14 proton, 14 neutron

Germanium – 32 proton, 32 neutronGermanium – 32 proton, 32 neutron

Atomic Structure

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Atomic StructureAtomic Structure

In the atom there is a maximum of In the atom there is a maximum of seven layers of the orbit (shell)seven layers of the orbit (shell)

the layer is known as K, L, M, N, the layer is known as K, L, M, N, O, P and Q O, P and Q

maximum number of electron in maximum number of electron in the orbit is determined by the orbit is determined by formula:formula:

2 x n²

n – number of the layer

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Maximum number of electrons:Maximum number of electrons:layer K (1)layer K (1) : 2n x 1: 2n x 1²²= = 22

layer L (2)layer L (2) : 2n x 2: 2n x 2²²= = 88

layer M (3)layer M (3) : 2n x 3: 2n x 3²²= = 1818

layer N (4)layer N (4) : 2n x 4: 2n x 4²²= = 3232

layer O (5)layer O (5) : 2n x 5: 2n x 5²²= = 5050

layer P (6)layer P (6) : 2n x 6: 2n x 6²²= = 7272

layer Q (7)layer Q (7) : 2n x 7: 2n x 7²²= = 9898

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+13 2 + 8 + 3 = 13

Layer K = 2 electron

layer L = 8 electron

layer M = 3 electron

Aluminium = 13 electron

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Outer layer of atom is called valence shell

There is not more than 8 electrons valence in this layer

Electron in this layer is called– electron valence

Number of electron valence determine the electrical characteristic of the material.

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Trivalence Atom .

3 electron valence

Indium, Boron dan Aluminium

Pentavalence Atom .

5 electron valence

Antimony (Sb), arsenic (As)

Neutral Atom :-

Number of proton = number of electron

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Materials that have a very Materials that have a very low resistance and therefore low resistance and therefore

pass current easilypass current easily

i.i. ConductorConductor

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1. Low resistance, current can easily flow

2. Atom is more tend to release its electron valence

3. This Electron can move from one to another atom freely .

1 – 3 electron valence

ii. Conductor characteristic

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Materials that have a very Materials that have a very high resistance and high resistance and threfore oppose currentthrefore oppose current

ii.ii. InsulatorInsulator

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1. Current cannot flow through2. High resistance3. Receives electrons from atomic

valence of other atoms to fill the valence levels and make it stable and free of any electrical activity @ chemistry

5 – 8 elektron valens

ii. Insulator characteristic

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iii.iii. SemiconductorSemiconductor

Neither a conductor nor a insulatorNeither a conductor nor a insulator

They can be controlled to either They can be controlled to either increase their resistance and behave increase their resistance and behave more like an insulator or more like an insulator or

decrease their resistance and decrease their resistance and behave more like a conductorbehave more like a conductor

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Have 4 electron valenceHave 4 electron valence

1. Neither a conductor nor a insulator

2. not easily release or received electron valence to/from other atom

iii. Semiconductor

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Silicon dan GermaniumSilicon dan Germanium

1432

Layer (M) – Layer Valens = 4

Layer (N) – Layer Valens = 4

layer(K) = 2 x 1 = 2

layer(L)

2 x 4 = 8

Layer (M)

2 x 9 = 18

No. atom Germanium = 32

2 + 8 + 18 + 4 = 32No.atom silikon = 14

2 + 8 + 4 = 14

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Covalent bond Covalent bond

When two or more When two or more similar semiconductor similar semiconductor atoms are combined to atoms are combined to form a solid element. form a solid element. They will share its 4 They will share its 4 electron valence with electron valence with its neighbouring atom. its neighbouring atom.

Si Si

Si Si Si

Si

Si Si Si

Covalent bond

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N –type N –type and and PP -type -type semiconductor semiconductor characterisriccharacterisric

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N-typeN-type

when Silicon @ when Silicon @ Germanium semiconductor Germanium semiconductor is dopped with pentavalen is dopped with pentavalen (Arsenic) impurity, there is (Arsenic) impurity, there is extra 1 electronextra 1 electronThis material is called N This material is called N typetype

Si Si

Si As Si

Si

Si Si Si

Covalent bond

Extra 1 electron

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P typeP type

When semiconductor When semiconductor Silicon or Germanium Silicon or Germanium doped with trivalent doped with trivalent impurities (indium), impurities (indium), shortage of an shortage of an electron.electron. Hol exist, charged + Hol exist, charged + veve This Semiconductor This Semiconductor becomes more hole becomes more hole This material is This material is called P type called P type

Si Si

Si In Si

Si

Si Si Si

Shortage of an electron

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P type

Figure 7

P type P type characteristiccharacteristic

Semiconductor is dopped Semiconductor is dopped with impurities with 3 with impurities with 3 electron valenceelectron valenceCurrent majority carrier is Current majority carrier is holeholeCurrent minority carrier is Current minority carrier is electronelectron

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Semiconductor is dopped Semiconductor is dopped with impurities with 5 with impurities with 5 electron valenceelectron valenceCurrent majority carrier is Current majority carrier is electronelectronCurrent minority carrier is Current minority carrier is holehole

N type

Figure 6

N type N type characteristiccharacteristic

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N P

Figure 5

P-N junctionP-N junction

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Depletion Region

Barrier Voltagei. Germanium = 0.3V

ii. Silicon = 0.7V

N P

Rajah 6

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What happen when What happen when junction builds up junction builds up

Electron in the n type Electron in the n type become attracted to fill the become attracted to fill the hole in the p type side.hole in the p type side.

Crossing of electrons occurs Crossing of electrons occurs from the N-type to the P-from the N-type to the P-type type


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This electron-Hole This electron-Hole combination makes the atoms combination makes the atoms near the grafts to be neutral.near the grafts to be neutral. After a while an area with no After a while an area with no current carriers exists .current carriers exists .


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Crossing of electrons will Crossing of electrons will stopstop

This area is called depletion This area is called depletion regionregion

Only small resistance Only small resistance between the 2 combined between the 2 combined material to form depletion material to form depletion regionregion


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Potential difference between Potential difference between p-n junction is known as p-n junction is known as barrier voltage. barrier voltage.

Barrier voltage Barrier voltage :-:-- - Germanium = Germanium =

0.3V0.3V- - Silikon Silikon = =

0.7V0.7V



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1. Biasing Voltage

voltage supplied to p-n junction

2 types of biasing :-

i. Forward biased

ii. Reversed biased

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i.i. Forward Forward biasedbiased

Definition :-Definition :-

negative source negative source connected to n-type connected to n-type

and and

positive source positive source connected to p-typeconnected to p-type

1. Biasing Voltage

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i. Depletion region become thinner, smaller

ii. Resistance becomes lowiii. Current can pass through

N-type

Figure 7

P-type

i. Forward Biased

1. Biasing Voltage

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Definition:-Definition:-

N-type material receives N-type material receives positive voltage supply positive voltage supply and p-type receives and p-type receives negative voltage supplynegative voltage supply

ii. Reverse Biased

1. Biasing Voltage

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i. Depletion region becomes widerii. Resistance becomes higheriii. Current cannot pass through

N-type

Figure 8

P-type

1. Biasing Voltage

ii. Reverse Biased

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2. Leakage Current

Minority current in the material.Minority current in the material. Exist when p-n combination Exist when p-n combination

receives reverse biased voltagereceives reverse biased voltage Electrons inside p-type material Electrons inside p-type material

will be pushed by biased voltage will be pushed by biased voltage towards the junction and across towards the junction and across it. it.

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2. Leakage Current

Produce a very small of current Produce a very small of current flow.flow.

This current is called leakage This current is called leakage voltage or reverse currentvoltage or reverse current

The value depends on The value depends on temperature . Smaller the temperature . Smaller the temperature value, the current temperature value, the current will be smaller too and vice will be smaller too and vice versa. versa.

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3. Breakdown Voltage

If the combined p-n supplied with If the combined p-n supplied with a very high reverse biased a very high reverse biased voltage, it will disturb the stability voltage, it will disturb the stability of covalent bond. of covalent bond.

Electrons will attracted to positive Electrons will attracted to positive potential and become free as a potential and become free as a current carriercurrent carrier

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This evolved electrons would violate This evolved electrons would violate other bond.other bond.

The result was a high value reverse The result was a high value reverse current flow current flow

The voltage where the breakdown The voltage where the breakdown occurs is called breakdown voltageoccurs is called breakdown voltage

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The p-n juntion will burnThe p-n juntion will burn

The voltage is the maksimum The voltage is the maksimum voltage of the junction when voltage of the junction when reverse biased Voltanreverse biased Voltan

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Contoh-contoh soalanContoh-contoh soalan

1.1. Lukiskan rajah struktur atom bagi :Lukiskan rajah struktur atom bagi :

a.a. Germanium mempunyai no atom 32.Germanium mempunyai no atom 32.

b.b. Silikon yang mempunyai no atom 14.Silikon yang mempunyai no atom 14.

Serta nyatakan sifat bahan-bahan Serta nyatakan sifat bahan-bahan tersebut .tersebut .

2. Apakah Ikatan Kovelen dan lukiskan rajah yang menunjukkan Ikatan kovelen bagi Germanium

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3.3. Berikan 4 faktor yang membolehkan Berikan 4 faktor yang membolehkan elektron terbebas dari ikatan Kovelenelektron terbebas dari ikatan Kovelen

4.4. Untuk membolehkan bahan jenis N Untuk membolehkan bahan jenis N dan P terhasil, semikonduktor tulen dan P terhasil, semikonduktor tulen perlu diserapkan dengan bendasing. perlu diserapkan dengan bendasing. Apakah bendasing itu dan terangkan Apakah bendasing itu dan terangkan setiap satu dan berikan contoh rajah setiap satu dan berikan contoh rajah yang menerangkan semikonduktor yang menerangkan semikonduktor tulen yang diserapkan dengan salah tulen yang diserapkan dengan salah satu bendasingsatu bendasing

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5.5. Nyatakan pembawa arus majoriti dan Nyatakan pembawa arus majoriti dan minoriti bagi bahan jenis N dan P.minoriti bagi bahan jenis N dan P.

6.6. Lukiskan dan jelaskan secara ringkas Lukiskan dan jelaskan secara ringkas maksud voltan pincang hadapan dan maksud voltan pincang hadapan dan voltan pincang songsangvoltan pincang songsang

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