Matter

Matter is anything that has mass and occupies space.

It is the substance that makes up everything in the universe, from the tiniest subatomic particles to the largest celestial bodies.

Matter is typically classified into several categories based on its properties, such as:

1. Solid
2. Liquid
3. Gas
4. Plasma

These categories depend on factors such as the arrangement of atoms or molecules and the strength of their interactions.

Molecule

A molecule is a group of two or more atoms that are chemically bonded together.

These atoms can be of the same element or different elements.

When atoms come together to form molecules, they do so through chemical bonds, which involve the sharing or transfer of electrons between atoms.

Molecules are the smallest units of compounds that retain the chemical properties of those compounds.

Example: Water is a molecule made up of two hydrogen atoms and one oxygen atom.

H₂O

Atom

An atom is the basic unit of a chemical element, consisting of a nucleus surrounded by one or more electrons.

The nucleus contains:

• Protons, which have a positive charge.
• Neutrons, which have no charge.

The electrons have a negative charge and orbit the nucleus in specific energy levels or shells.

Atoms can combine with other atoms through chemical bonds to form molecules and compounds.

These bonds are created when atoms share, lose, or gain electrons, resulting in stable arrangements known as molecules or compounds.

Introduction to KCL and KVL

Kirchhoff’s Law

Ohm’s Law is used to analyse current, voltage, and resistance in simple circuits, but Kirchhoff’s Law can be used to calculate values in complex circuits.

There are two Kirchhoff’s laws:

1. Kirchhoff’s Current Law
2. Kirchhoff’s Voltage Law

1. Kirchhoff’s Current Law

This law is also known as:

• Kirchhoff’s First Law
• Kirchhoff’s Junction Law

According to the statement:

“In a closed network of conductor, the algebraic sum of current meeting at a node is point.”

Alternatively, current flowing towards a junction in a closed network system is equal to the current flowing away from the same junction.

Current exiting a junction will have a negative sign if the current entering the junction has a positive sign.

KCL Equation

For the figure shown above, applying KCL at the node, we get:

I₁ + I₂ + I₃ = I₄ + I₅

Or,

I₁ + I₂ + I₃ – I₄ – I₅ = 0

This can be generalized to the case with n wires all connected at a node.

Figure: Add KCL junction diagram here.

2. Kirchhoff’s Voltage Law

This law is also known as:

• Kirchhoff’s Second Law
• Kirchhoff’s Loop Law

It states:

“In a closed loop, the algebraic sum of all the potential differences is zero.”

Alternatively, in any closed loop, the algebraic sum of all electromotive forces of sources and potential drops in the load is equal to zero.

While moving from lower potential to higher potential, there is a gain in potential difference. Therefore, the potential difference in the direction of movement is taken as positive.

While moving from higher potential to lower potential, there is a fall in potential. Therefore, the potential difference in the direction of movement is taken as negative.

KVL Equation

For the figure shown above, applying KVL in the loop, we get:

R₁ + R₂ + R₃ + R₄ + R₅ = Vₛ

Or,

R₁ + R₂ + R₃ + R₄ + R₄ – Vₛ

KVL can be generalized to any loop containing any number of components.

Figure: Add KVL loop diagram here.

Introduction to Semiconductor Material

Semiconductors are substances with conductivity that is intermediate between metals and insulators.

The most common semiconductor material is silicon.

Other semiconductor materials include:

• Germanium
• Gallium arsenide
• Other semiconductor materials

Semiconductors are used in a wide range of applications such as:

• Electronic devices
• Solar cells
• LED lights
• Sensors

There are two types of semiconductors:

1. Intrinsic Semiconductor
2. Extrinsic Semiconductor

A. Intrinsic Semiconductor

An intrinsic semiconductor is a pure semiconductor.

It does not have any impurities added to it.

In an intrinsic semiconductor, the number of free electrons and holes is equal.

Examples of intrinsic semiconductors include:

• Silicon
• Germanium

Figure: Add intrinsic semiconductor diagram here.

B. Extrinsic Semiconductor

An extrinsic semiconductor is a semiconductor that has been intentionally doped with impurities to alter its electrical properties.

Figure: Add extrinsic semiconductor diagram here.

Doping

The conductivity of a semiconductor is increased by adding an appropriate amount of suitable impurities.

This process is known as doping.

Based on the type of impurities added, extrinsic semiconductors are classified into two types:

1. N-type Semiconductor
2. P-type Semiconductor

N-Type Semiconductor

An N-type semiconductor is doped with impurities that have more electrons than the intrinsic semiconductor.

It is referred to as an N-type semiconductor when a pentavalent impurity atom is added to an inherent semiconducting atom such as silicon or germanium.

Figure: Add N-type semiconductor diagram here.

P-Type Semiconductor

A P-type semiconductor is doped with impurities that have fewer electrons than the intrinsic semiconductor.

It is referred to as a P-type semiconductor when a trivalent impurity atom is added to an inherent semiconducting atom such as silicon or germanium.

Figure: Add P-type semiconductor diagram here.

Majority and Minority Charge Carrier

There are two types of charge carriers discussed in semiconductor material:

1. Majority Charge Carrier
2. Minority Charge Carrier

Majority Charge Carrier

Majority charge carriers are the most abundant type of charge carriers in a semiconductor.

They are created by doping the semiconductor with impurities that either introduce excess electrons or create vacancies for electrons.

Majority carriers in P-type semiconductors are holes.

Figure: Add majority charge carrier diagram here.

Minority Charge Carrier

Minority charge carriers are present in smaller quantities than the majority carriers.

They are created by thermal excitation or by the action of external sources such as light.

According to the provided notes, minority carriers in an N-type semiconductor are stated as free electrons.

Figure: Add minority charge carrier diagram here.

PN Junction Formation

A PN Junction is a type of semiconductor junction that is formed by bringing together a P-type semiconductor and an N-type semiconductor.

To form a PN junction, we take:

P-Type Semiconductor

It has:

• Majority carriers: Holes
• Minority carriers: Electrons

N-Type Semiconductor

It has:

• Majority carriers: Free electrons
• Minority carriers: Holes

The P-type and N-type semiconductor materials are joined with the help of a special fabrication technique.

When these two materials are joined together, a junction is formed known as a PN Junction.

Figure: Add PN junction formation diagram here.

Forward Bias

When the P-type region of a PN junction is connected to the positive terminal of a battery and the N-type region is connected to the negative terminal, it is said to be Forward Bias.

Connection:

P-type → Positive terminal

N-type → Negative terminal

Figure: Add forward bias PN junction diagram here.

Reverse Bias

If an external voltage is applied with the positive terminal connected to the N-side and the negative terminal connected to the P-side, then the junction is said to be Reverse Bias.

Connection:

N-type → Positive terminal

P-type → Negative terminal

Figure: Add reverse bias PN junction diagram here.