Electronics: Semiconductor Materials and Devices

Course Content

• The course covers semiconductor materials and properties, diodes and applications, transistors as amplifiers and switches, operational amplifiers, and more.
• The grading system includes exams (70%), mid-semester exams (10%), assignments (10%), quizzes (5%), and lab work/simulation (5%).
• The recommended software is Multisim.

Carrier Mobility

• Carrier mobility is a measure of how easily a carrier moves in a particular material, expressed in cm²/Vs.
• Carrier mobility (µ) is the drift velocity per unit field.

Drift Current

• Drift current is produced by the motion of electrons and holes under an electric field.
• The net current is always in the direction of the applied electric field.

Current Density

• Current density (J) is the amount of charge crossing a plane unit area per unit time.
• For a semiconductor with an applied electric field, the total drift current is J_drift = J_n(drift) + J_p(drift).

Conductivity

• When an electric field E is applied to a semiconductor, the free electrons drift with average velocity ve = -µeE, where µe is the electron mobility.

Introduction to Electronics

Capacitors

• Capacitors charge and hold the charge as long as the DC voltage is applied.
• Capacitors block DC current from passing through and pass AC.
• The unit of capacitance is the farad.

Inductors

• Inductors store energy in a magnetic field.
• Inductance is measured in Henry(s).
• Factors affecting inductance include the number of coil turns, diameter of coil, spacing between turns, and size of the wire used.
• Inductors can be air wound, wound around a permeable material, or wound around a circular form (toroid).

Transformers

• Transformers can be used to step up or step down AC voltage.

Semiconductor Materials and Properties

Conductors, Insulators, and Semiconductors

• Electronic materials can be classified into conductors, insulators, and semiconductors.
• Conductors have low resistance, insulators have high resistance, and semiconductors can allow or suppress electrical current flow.

Energy Bands

• The difference in conductivity between electronic materials can be explained with the help of energy bands.
• Insulators have a large energy difference between conduction and valence bands, conductors have overlapping conduction and valence bands, and semiconductors have a small energy difference between conduction and valence bands.

Conductors

• Good conductors have low resistance, and electrons flow through them with ease.
• Examples of good conductors include copper, silver, gold, aluminum, and nickel.

Temperature Sensitivity

• In both types of extrinsic semiconductor, temperature variations make little difference to conductivity.
• For intrinsic conductivity, the number of carriers and thus increases rapidly with temperature.

Diffusion Current

• Diffusion current is the directional movement of charge carriers due to their concentration gradient.
• It is encountered only in semiconductors and is normally absent in conductors.
• Diffusion current is produced due to the concentration gradient of charge carriers.