Understanding Ideal Diodes and Semiconductor Materials

Ideal Diodes

What is the main difference between a simple key and an ideal diode?

A: The ideal diode can drive in a single direction.

Semiconductor Materials

Semiconductor, Resistivity, Resistance, and Ohmic Contact

A: A semiconductor is a material with a conductivity level between a conductor and an insulator.

Resistivity is a measure of how readily a material allows the passage of an electric charge. Lower resistivity indicates a material that easily conducts electricity. It's used to compare the resistance levels of different materials.

Atomic Structure of Copper and Conductivity

What makes copper a good conductor is that its valence electrons (copper has one electron in its outermost layer) are weakly bound to the atom and can be easily moved.

Intrinsic, Extrinsic, Covalent, and Negative Temperature Coefficient

A: Intrinsic semiconductors have a very low level of impurities.

Extrinsic semiconductors are created through a doping process.

A covalent bond is a connection established by the sharing of electrons between neighboring atoms.

A negative temperature coefficient means that resistance falls with increasing temperature.

Extrinsic Semiconductors: N-Type and P-Type

Difference Between N-Type and P-Type Semiconductors

R: N-type material is formed by adding donor atoms with 5 valence electrons, establishing a high level of relatively free electrons.

The electron is the majority carrier, and the hole is the minority carrier.

P-type material is formed by adding acceptor atoms with three valence electrons, establishing a high level of holes in the material.

The hole is the majority carrier, and the electron is the minority carrier.

Donor and Acceptor Impurities

R: Donor impurities are diffused with 5 valence electrons.

Acceptor impurities are diffused with three valence electrons.

Minority and Majority Carriers

The majority carrier is the carrier that prevails in the material.

The minority carrier is the carrier present in the smallest number in the material.

Semiconductor Diodes

Forward and Reverse Bias in a PN Junction Diode

A: Forward bias means the current in the diode increases exponentially with increasing voltage across the diode.

Reverse bias means the current in the diode is reverse saturation (almost doubles in value for each 10°C increase in temperature), which is very small, until there is a breakdown, and Zener current flows in the opposite direction indicated by the diode.

Threshold Voltage

• Silicon: 0.7 V - up to 200 °C
• Germanium: 0.3 V up to 100 °C

The only disadvantage of silicon is the larger direct bias voltage required to reach the highest region of conduction.