Semiconductor Diode Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. Semiconductor diodes can be used as a _______.

1. Amplifier
2. Oscillator
3. Modulator
4. Rectifier

Ans. The correct answer is d. Rectifier

Explanation: A semiconductor diode can be used as a rectifier that converts alternating current to direct current.

Ques. Who made the first semiconductor diode?

1. Sir Issac Newton
2. John Ambrose Fleming
3. Ferdinand Braun
4. Georg Simon Ohm

Ans. The correct answer is c. Ferdinand Braun

Explanation: German physicist Ferdinand in 1874 was the first to discover asymmetric electrical conduction across the contact between a crystalline mineral and a metal.

Ques. Who discovered the PN junction?

1. Georg Simon Ohm
2. Russell Ohl
3. Sir Issac Newton
4. Physicist Ferdinand Braun

Ans. The correct answer is b. Russell Ohl

Explanation: Russell Ohl was the first who discovered p-n junction.

Ques. What is a semiconductor diode?

Ans. A semiconductor diode is a two-terminal device that consists of a p-n junction having metallic contacts at both ends. It conducts current only in one direction.

Ques. What is a Zener diode used as?

1. Rectifier
2. Oscillator
3. Filter
4. Regulator

Ans. The correct answer is d. Regulator

Explanation: Zener diode is a semiconductor diode that works in the breakdown region without damaging itself. It is mainly used as a voltage regulator.

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Short Answers Questions [2 Marks Questions]

Ques. What are the types of semiconductor diodes?

Ans. The different types of semiconductor diodes are

• Light emitting diode (LED)
• Rectifier diode
• Variable capacitance diode
• Zener diode
• Gunn diode
• Tunnel diode
• Switching diode
• Photodiode

Ques. Why are semiconductor diodes non-ohmic?

Ans. According to Ohm’s law, there is a linear relationship between the voltage and current. The material that has a linear relationship between voltage and current is known as ohmic material and the material that does not have a linear relationship between voltage and current is known as non-ohmic material.

A semiconductor diode does not have a linear relationship between voltage and current. Therefore they are said to be non-ohmic.

Ques. What is a p-type and n-type semiconductor?

Ans. When a suitable trivalent impurity is added to pure germanium or silicon we get an extrinsic semiconductor, known as a p-type semiconductor. In p-type semiconductor majority of charge carriers are holes.

When a suitable pentavalent impurity is added to pure germanium or silicon we get an extrinsic semiconductor, known as a n-type semiconductor. In n-type semiconductor majority of charge carriers are electrons.

Ques. What are the two types of semiconductors?

Ans. There are two types of semiconductors. They are

• Intrinsic Semiconductor
• Extrinsic Semiconductor

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Long Answers Questions [3 Marks Questions]

Ques. What are the applications of semiconductor diodes?

Ans. The applications of semiconductor diodes are:

• Semiconductor diodes are used as rectifier diode which converts alternating current to direct current.
• It is used as a Zener diode for the stabilization of voltage or current.
• It is used as a photodiode to detect the intensity of radiation or light.
• A light-emitting diode (LED) is used to convert electrical energy to light energy.
• Switching diode which is used for fast switching requirements.

Ques. What is the composition of a Semiconductor Diode and what are its characteristics? 

Ans. A semiconductor diode is commonly made from silicon. A negatively charged cathode that has an excess of electrons is placed near the positively charged anode that has an excess of holes. A depletion region is developed between the cathode and anode where no electrons and holes were present. A diode has a forward voltage, forward current, reverse voltage, and current as its characteristics.

Ques. What is forward biasing and reverse biasing of a semiconductor diode?

Ans. A semiconductor diode is said to be forward-biased when the positive terminal of the cell is connected to the p-side and the negative terminal of the cell is connected to the n-side of the semiconductor diode.

A semiconductor diode is said to be reverse-biased when the positive terminal of the battery is connected to the n-side and the negative terminal of the battery is connected to the p-side of the semiconductor diode.

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Very Long Answers Questions [5 Marks Questions]

Ques. What is LED? Write its advantages and uses.

Ans. A special heavily doped p-n junction semiconductor diode that emits spontaneous radiation when forward biased is known as a light emitting diode (LED).

• A light-emitting diode converts electrical energy into light energy.
• LEDs made of compound semiconductors like GaAs and GaAsP emits energy in different forms.

The following are the advantages of LED

• It is easy to manufacture
• It works at a lower voltage
• It consumes very less power
• Longer life
• Low cost

The following are the uses of LED

• It is used in CD players, laser printers, etc.
• It is used as an indicator lamp
• It is used in digital displays in watches and calculators
• It is used in night lamps, flash lamps, and torch lamps.

Ques. What are the forward bias and reverse bias characteristics of semiconductor diodes?

Ans. The variation of current with the applied voltage across the junction diode gives the characteristics of semiconductor diodes.

Forward bias characteristics:

When the battery voltage is zero, the diode does not conduct due to the junction potential barrier. When the voltage is applied across the diode, the barrier potential starts decreasing. Thus, a small current begins to flow. As the voltage increases the forward current increases rapidly. The battery voltage at which the forward current starts increasing rapidly is known as the knee voltage or threshold voltage or cut-in voltage.

Reverse bias characteristics:

When a semiconductor diode is reverse-biased, the majority of carriers in the p and n regions are repelled away from the junction. Therese is a small current due to minority carriers. As the reverse voltage is increased to a certain value called breakdown voltage, there is a sudden rise in reverse current.

Once breakdown voltage is reached any increase in the applied voltage leads to the high reverse current which may damage the semiconductor diode.

The forward and reverse biased characteristics of a semiconductor diode are shown below

Ques. Explain the formation of the depletion region in the semiconductor diode.

Ans. The region around the p-n junction of a semiconductor diode that has no mobile charge carriers is known as the depletion region or depletion layer.

Holes diffuse through the junction from high concentration to low concentration region and get neutralized. Similarly, electrons diffuse through the junction from the n-region to the p-region and get neutralized.

When holes diffuse through the junction, the region of the junction is left with negative ions which remain fixed in their position. Also, when electrons diffuse through the junction, the region near the junction is left with positive ions, which remain fixed.

This space charge region on both sides forms a depletion layer or region because it has no mobile charges.

The potential difference due to negative immobile ions on the p-side of the junction and positive immobile ions on the n-side of the junction is called the potential barrier or junction barrier.

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