[ AETN2101 ] 2 - Diodes

Two terminals.

How many terminals does a semiconductor diode have?

One direction.

Ideally, in how many directions does a diode conduct current?

It acts as a short circuit, allowing current to flow.

Ideal Diode in Forward Bias

It acts as an open circuit, preventing current flow (ID​=0).

Ideal Diode in Reverse Bias

False (it has high resistance due to very few free electrons or holes).

True or False: An intrinsic semiconductor (not doped) has low resistance.

They are doped with donors, providing many free electrons.

Why do N-type semiconductors have low resistance?

Acceptors (which provide many holes).

P-type semiconductors have low resistance because they are doped with _____.

Silicon (Si), Germanium (Ge), and Gallium Arsenide (GaAs).

List three materials commonly used in the development of semiconductor devices.

By doping one end as p-type material and the other end as n-type material.

How is a p−n junction formed in a single crystal?

The formation of the depletion region.

What occurs when free electrons from the n-type material flow into and fill holes in the p-type material near the junction?

The depletion region has very high resistance.

In terms of resistance, how does the depletion region compare to doped p-type or n-type material?

It lacks extra free electrons and holes due to the recombination of carriers.

Why does the depletion region behave like an intrinsic semiconductor?

Barrier (or V0​).

The potential difference that exists across the depletion layer is known as the _____ potential.

B) 0.7V

What is the typical barrier potential (V0) for Silicon?

A) 0.3V

B) 0.7V

C) 1.1V

C) 0.3V

What is the typical barrier potential (V0) for Germanium?

A) 0.1V

B) 0.7V

C) 0.3V

No bias, Reverse bias, and Forward bias.

List the three operating conditions of a diode.

0A.

Under the 'No Bias' condition, what is the value of the diode current (ID​)?

It causes the depletion region to widen.

How does applying a reverse bias voltage affect the width of the depletion region?

True.

True or False: In a reverse-biased diode, electrons in the n-type material are attracted toward the positive terminal of the external voltage.

Leakage current (or Is​).

What is the name of the current that flows in a diode under reverse bias before breakdown occurs?

Minority carriers.

Which type of charge carriers are responsible for the small leakage current (Is​) in reverse bias?

It may be destroyed and allow significant current to flow in the reverse direction.

What happens to a real diode if excess voltage is applied in the reverse direction?

The specific reverse voltage level at which a diode's resistance drops sharply, potentially destroying the device.

Breakdown Voltage

Avalanche current.

In the practical diode characteristic curve, what is the current called that flows immediately after breakdown?

True (according to the ideal model plot).

True or False: In an ideal diode characteristic, the reverse current is always exactly zero regardless of the reverse voltage magnitude.

A voltage source (VK​), a resistor (rav​), and an ideal diode.

Identify the three components used in the diode equivalent circuit model shown in the lecture.

10Ω.

In the provided diode equivalent circuit, what is the typical value for the internal resistance rav​?

0.7V.

In the provided diode equivalent circuit for Silicon, what is the value of the knee voltage (VK​)?

Light-Emitting Diode.

What does the abbreviation LED stand for?

Forward bias.

Under what biasing condition does an LED emit photons?

The type of material used in doping.

What factor determines the specific color of light emitted by an LED?

2V to 3V.

What is the typical range for the forward bias voltage of an LED?

Carriers (electrons in N-type, holes in P-type) that are pushed toward the junction by the external voltage to reduce the depletion width.

Majority Carriers in Forward Bias

True.

True or False: A diode array is considered a 'different' or 'other' type of diode configuration compared to a single discrete diode.

Greater than zero (VD​>0).

According to the ideal diode model, the diode conducts current when VD​ is _____.

0V.

In the 'No Bias' state, the external voltage VD​ is equal to _____.

Free electrons.

What is the primary charge carrier in N-type semiconductor material?

Holes.

What is the primary charge carrier in P-type semiconductor material?

B) Intrinsic semiconductor

The depletion region acts most like which type of material?

A) Conductor
B) Intrinsic semiconductor
C) N-type semiconductor

They are attracted toward the negative terminal of the voltage source, away from the junction.

What happens to the majority carriers in the p-type material during reverse bias?

False (Gallium Arsenide is also commonly used).

True or False: Silicon and Germanium are the only materials used to create diodes.

The n-type side (because free electrons have left).

In a p−n junction diagram, which side typically accumulates a relative positive charge in the depletion zone?

The p-type side (because holes are filled/compensated by electrons).

In a p−n junction diagram, which side typically accumulates a relative negative charge in the depletion zone?

To develop a working knowledge of the diode in various configurations appropriate for specific applications.

What is the purpose of using models like the 'Diode Equivalent Circuit'?

Is​.

The symbol for current in the reverse direction (leakage current) is often denoted as _____.

C) Intrinsic material

Which of the following has the highest resistance?

A) N-type material
B) P-type material
C) Intrinsic material

True.

True or False: Imajority​ is equal to zero during reverse bias.

Barrier potential.

In the context of diodes, what does the variable V0 ​ represent?

Light-emitting diodes (LEDs) and Diode arrays.

List the two main 'Other Diodes' mentioned at the end of the lecture.

The practical curve shows a gradual increase in current after the barrier potential is reached, rather than an instant vertical line at zero volts.

How does the 'practical characteristic' curve of a diode differ from the 'ideal characteristic' in the forward direction?

No, the voltage must typically exceed the barrier potential to overcome the depletion region's resistance.

If a diode is forward biased but the voltage is less than V0​, will significant current flow?

Increased doping with donors or acceptors lowers the semiconductor's resistance.

What is the relationship between doping and semiconductor resistance?

Photons.

In an LED, the process of emitting light involves the release of particles called _____.

The average AC or dynamic resistance of the diode when it is conducting current.

rav​ in Diode Models

The negative terminal.

Which terminal of the voltage source is connected to the p-side of a diode to achieve reverse bias?

The positive terminal.

Which terminal of the voltage source is connected to the n-side of a diode to achieve reverse bias?

True.

True or False: The depletion region is physically located exactly at the interface of the p and n materials.

Knee voltage (equivalent to the barrier potential).

What does the symbol VK​ stand for in the practical diode model?

B) Compound semiconductor

Gallium Arsenide is categorized as a:

A) Pure element
B) Compound semiconductor
C) Insulator

They are filled or compensated by free electrons flowing from the n-type material.

What happens to the 'holes' in the p-type material near the junction when the p−n junction is first formed?