ELECTRONICS I

Instructor: Eng.Moayed N. EL Mobaied

The Islamic University of GazaFaculty of EngineeringElectrical Engineering Department

الرحمن الله بسمالرحيم

EELE 2321 — Spring 2010

Lecture 2

Semiconductor materials

Materials

Conductor Insulator Semiconductor

Cupper, Gold, Aluminum …etc

Wood , Mica, Plastic…etc

Silicon,Germanium …etc

Semiconductor materials

Atoms

Electron(-) Proton(+) Neutron (No)

Proton +Neutron= Nucleus

Semiconductor materials

Conductor

Cupper

Semiconductor materials

Semiconductor

Silicon

Semiconductor materials

Idea : Electronics are how to control of 1- Current pass 2- Current flow

(Semiconductors)

Semiconductor materials

(Semiconductors)

Compound –crystal

Silicon

Single –crystal

Germanium Gallium arsenide

Gallium Nitride

Si Ge GaAs GaN

Germanium: (1947) Easy to find. Sensitive to changes in temperature.

Silicon: (1954)

Less sensitive to changes in temperature. Widely used.

Gallium arsenide: ( 1970)

Speed of operation up to 5 times Si. More expensive.

Semiconductor materials

Semiconductor materials

Silicon = 14Germanium = 32

Gallium = 31Arsenic = 33

4 valence= tetravalent 5 valence= pentavalent Valence : Potential (ionization potential) less than other electrons in other shell.

Semiconductor materials

Covalent bonding

Pure silicon

Single-crystal

8 Electrons in outside

doping

Intrinsic

Extrinsic

Semiconductor materials

Covalent bonding

GaAs

Compound-crystal

Semiconductor materials

Covalent bonding

Valence electrons

Absorb kinetic energy

Break Covalent bond

Free state

Very sensitive to any applied electric fields

Thermal energyLight energy

Intrinsic carriers = Free electron due to external causes

Semiconductor materials

semiconductorIntrinsic Carriers

(per cubic centimeter)

GaAs1.7*106

Si1.5*1010

Ge2.5*1013

Semiconductor materials

semiconductorRelative mobility factor

(µn )

Si1500

Ge3900

GaAs8500

Ability of the free carriers to move throughout the material

Semiconductor materials

Conductors: Positive temperature coefficient ( # carriers slightly increase in heat, But their vibration pattern about a

relatively fixed location make it difficult to flow through the material)

Semiconductors : Negative temperature coefficient (kinetic energy)

Semiconductor materials

Energy level

Semiconductor materials

Energy level

End of Lecture **** Eng.moayed