Semiconductor Physics And Electronic Devices
- 1.
Is operating temperature range of ICs, computers and other semiconductor devices conditioned by the used semiconductor material's band gap?
- A.
Yes, the more the band gap, the more temperature range
- B.
No, as concentration of minority charge carriers is independent from temperature
- C.
Conditioned partially as by increasing the temperature, carriers' mobility decreases
- D.
No, as band gap does not depend on temperature
- E.
The correct answer is missing
Correct Answer
A. Yes, the more the band gap, the more temperature rangeExplanation
The operating temperature range of ICs, computers, and other semiconductor devices is conditioned by the used semiconductor material's band gap. The band gap refers to the energy difference between the valence band and the conduction band in a semiconductor. A larger band gap allows the material to withstand higher temperatures without the electrons in the valence band gaining enough energy to jump to the conduction band, which could lead to device failure. Therefore, a larger band gap corresponds to a wider temperature range in which the semiconductor device can operate reliably.Rate this question:
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- 2.
Which expression is wrong?
- A.
Diode subtypes are: point-junction diodes, stabilitrons, varicaps and tunnel diodes
- B.
In tunnel diodes reverse current for the same voltage is higher than direct current value
- C.
In varicaps with increase of voltage barrier capacitance increases
- D.
Schottky diodes operation is based on processes which take place in semiconductor-metal contact
- E.
The response time of Schottky diodes, therefore, frequency properties are conditioned by barrier capacitance
Correct Answer
C. In varicaps with increase of voltage barrier capacitance increasesExplanation
Varicaps are also known as variable capacitance diodes. In varicaps, the capacitance value changes with the applied voltage. As the voltage increases, the barrier capacitance decreases, not increases. Therefore, the statement "In varicaps with increase of voltage barrier capacitance increases" is incorrect.Rate this question:
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- 3.
Field effect transistors, compared with bipolar transistors
- A.
Have small input resistance
- B.
Have small noise coefficient
- C.
The current is at the same time conditioned by electrons and holes
- D.
Provide current amplification
- E.
The performance is mainly conditioned by injection of minority carriers
Correct Answer
B. Have small noise coefficientExplanation
Field effect transistors (FETs) have a small noise coefficient compared to bipolar transistors. This means that FETs produce less noise in their operation, making them more suitable for applications where low noise is desired, such as in audio amplifiers or sensitive electronic circuits. The noise coefficient is a measure of the amount of unwanted electrical signals or interference generated by a device, and a smaller coefficient indicates a lower level of noise. Therefore, FETs are preferred over bipolar transistors in situations where noise reduction is important.Rate this question:
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- 4.
Through which device is the electrical signal amplification implemented?
- A.
Resistor
- B.
Capacitor and inductor
- C.
Diode
- D.
Transistor
- E.
Photodiode
Correct Answer
D. TransistorExplanation
A transistor is a semiconductor device that can amplify electrical signals. It is commonly used in electronic circuits to amplify weak signals or switch electronic signals on and off. Unlike other devices listed, such as resistors, capacitors, inductors, diodes, and photodiodes, a transistor has the ability to provide significant signal amplification, making it the correct answer for this question.Rate this question:
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- 5.
How many pins does the field effect transistor have?
- A.
1 gate
- B.
2 sources and 1 drain
- C.
3 sources, 1 gates and 1 drain
- D.
2 bases and 1 collector
- E.
1 source, 1 gate and 1 drain
Correct Answer
E. 1 source, 1 gate and 1 drainExplanation
A field effect transistor (FET) typically has three pins: one source, one gate, and one drain. The source is where the current enters, the gate controls the flow of current, and the drain is where the current exits. Therefore, the correct answer is "1 source, 1 gate, and 1 drain."Rate this question:
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- 6.
Is the gate of a field effect transistor isolated from its channel?
- A.
Yes
- B.
No
- C.
Partially and there is weak tunnel coupling
- D.
In saturation mode of field effect transistor most part of channel current flows through gate
- E.
The correct answer is missing
Correct Answer
A. YesExplanation
Yes, the gate of a field effect transistor is isolated from its channel. This means that there is no direct electrical connection between the gate and the channel. The gate controls the conductivity of the channel by creating an electric field that attracts or repels charge carriers, thus modulating the channel current. This isolation is achieved by using a thin insulating layer, typically made of silicon dioxide, between the gate and the channel.Rate this question:
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- 7.
N – type Ge sample, which is anticipated for making a transistor, has 1.5 Ohmcm specific resistance and 5.4103 cm3/Kl Holy coefficient. What does the charge carriers' concentration and their mobility equal?
- A.
1.6*10^21 m-3, 5 m2/Vs
- B.
1.6*10^21 m-3, 0.1 m2/Vs
- C.
1.16*10^21 m-3, 0.36 m2/Vs
- D.
2*10^20 m-3, 0.36 m2/Vs
- E.
The correct answer is missing.
Correct Answer
C. 1.16*10^21 m-3, 0.36 m2/VsExplanation
The charge carriers' concentration in the n-type Ge sample is 1.16*10^21 m-3, which means there are 1.16*10^21 charge carriers per cubic meter. The mobility of the charge carriers is 0.36 m2/V*s, indicating how easily they can move in response to an electric field.Rate this question:
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- 8.
By means of what semiconductor device can light influence be detected?
- A.
Posistor
- B.
Resistor
- C.
Photodiode
- D.
Capacitor
- E.
Inductor
Correct Answer
C. PhotodiodeExplanation
A photodiode is a semiconductor device that can detect light influence. It operates by converting light energy into electrical current. When light falls on the photodiode, it generates electron-hole pairs, which create a current flow. This current can then be measured and used to detect the presence or intensity of light. Unlike other semiconductor devices listed, such as a resistor, capacitor, or inductor, a photodiode specifically designed for light detection and is commonly used in various applications like optical communication, light sensing, and imaging.Rate this question:
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- 9.
Which materials' conductivity is higher?
- A.
Dielectrics
- B.
Semiconductors
- C.
Metals
- D.
All have low conductivity
- E.
All have high conductivity
Correct Answer
C. MetalsExplanation
Metals have higher conductivity compared to dielectrics and semiconductors. This is because metals have a large number of free electrons that are able to move easily through the material, allowing for the flow of electric current. In contrast, dielectrics have very few free electrons and semiconductors have a moderate number of free electrons, resulting in lower conductivity.Rate this question:
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- 10.
How does the negative differential resistance current range change depending on the density of lightly degenerated n-region impurities in tunnel diode?
- A.
Interval decreases when increasing density
- B.
Interval increases when increasing density
- C.
It is not conditioned by density of impurity
- D.
Interval increases when reducing density
- E.
All the conditions are true
Correct Answer
B. Interval increases when increasing densityExplanation
The correct answer is "Interval increases when increasing density". This means that as the density of lightly degenerated n-region impurities in a tunnel diode increases, the range of negative differential resistance current also increases. This implies that the tunnel diode becomes more sensitive to changes in current as the impurity density increases.Rate this question:
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- 11.
Generally, what is the response time of photodiode conditioned by?
- A.
The diffusion time of equilibrium carriers in the base
- B.
Their transit time through the layer of p-n junction
- C.
RC constant of diode structure
- D.
Only A and C
- E.
Conditions A, B, C
Correct Answer
E. Conditions A, B, CExplanation
The response time of a photodiode is generally conditioned by the diffusion time of equilibrium carriers in the base, their transit time through the layer of p-n junction, and the RC constant of the diode structure. These three conditions affect the time it takes for the photodiode to respond to changes in incident light and generate an output signal.Rate this question:
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- 12.
Which statement mentioned below is not true for ohmic contact?
- A.
Electrical resistance of ohmic contact is small
- B.
Electrical resistance of ohmic contact does not depend on the current direction if the current value does not exceed the given value
- C.
Electrical resistance of ohmic contact does not depend on the current direction in case of any current value flowing through it
- D.
Most part of ohmic contacts is formed on the basis of n-n+ or p-p+ type contacts
- E.
All the answers are correct
Correct Answer
C. Electrical resistance of ohmic contact does not depend on the current direction in case of any current value flowing through itExplanation
The electrical resistance of an ohmic contact does not depend on the current direction in case of any current value flowing through it. This means that the resistance remains the same regardless of the direction of current flow. This is a characteristic of ohmic contacts, which have a linear relationship between current and voltage. In other words, the resistance remains constant regardless of the direction or magnitude of the current.Rate this question:
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- 13.
By increasing the lifetime of electrons 4 times, their diffusion length
- A.
Increases 4 times
- B.
Increases twice
- C.
Does not increase
- D.
Reduces twice
- E.
The correct answer is missing
Correct Answer
C. Does not increaseExplanation
Increasing the lifetime of electrons does not directly affect their diffusion length. The diffusion length is determined by other factors such as the material properties and the presence of impurities or defects. Therefore, increasing the lifetime of electrons will not have any effect on their diffusion length.Rate this question:
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- 14.
What does the generation frequency depend on in Gunn diode?
- A.
Mobility speed of field domain
- B.
Impurity density in semiconductor
- C.
Sample length
- D.
Dielectric permeability of material
- E.
All the answers are correct
Correct Answer
C. Sample lengthExplanation
The generation frequency in a Gunn diode depends on the sample length. The sample length determines the resonant frequency of the device, which is the frequency at which the diode oscillates. A longer sample length will result in a lower resonant frequency, while a shorter sample length will result in a higher resonant frequency. Therefore, the sample length plays a crucial role in determining the generation frequency of a Gunn diode.Rate this question:
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- 15.
How can the cutoff voltage of MOS transistor change?
- A.
By opposite voltage of substrate-channel junction, when substrate is higher ohmic than the channel
- B.
By opposite voltage of substrate-channel junction when substrate resistance is equal or smaller than the channel resistance
- C.
By voltage applied to the gate
- D.
By A and C
- E.
By B and C
Correct Answer
E. By B and CExplanation
The cutoff voltage of a MOS transistor can change by two ways: by the opposite voltage of the substrate-channel junction when the substrate resistance is equal or smaller than the channel resistance, and by the voltage applied to the gate.Rate this question:
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- 16.
Which statement is wrong for unipolar transistors?
- A.
In unipolar transistors, physical processes of current transport are conditioned by one sign carriers-electrons or holes
- B.
In unipolar transistors, physical processes of current transport are conditioned by the injection of minority carriers.
- C.
In unipolar transistors current control is carried out by the vertical electrical field
- D.
The surface channel unipolar transistor includes metal-dielectric-semiconductor structure
- E.
The correct answer is missing
Correct Answer
C. In unipolar transistors current control is carried out by the vertical electrical fieldExplanation
The statement "In unipolar transistors current control is carried out by the vertical electrical field" is incorrect. In unipolar transistors, current control is not carried out by the vertical electrical field. Unipolar transistors, also known as field-effect transistors (FETs), control current through the modulation of a charge carrier concentration in a semiconductor channel. This modulation is achieved by applying a voltage to the gate terminal, which creates an electric field that controls the flow of majority carriers (either electrons or holes) in the channel. The vertical electrical field does not play a role in current control in unipolar transistors.Rate this question:
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- 17.
What is the high frequency property of Schottky diode conditioned by?
- A.
Moving the majority carriers through diode
- B.
Excluding minority carriers’ accumulation in diode
- C.
Value of Schottky barrier
- D.
Impurity density in a semiconductor
- E.
Only C and D
Correct Answer
B. Excluding minority carriers’ accumulation in diodeExplanation
The high frequency property of a Schottky diode is conditioned by excluding the accumulation of minority carriers in the diode. This means that the diode is designed in a way that prevents the buildup of minority carriers, which allows for faster switching speeds and better high-frequency performance. The other options, such as moving majority carriers through the diode, the value of the Schottky barrier, and the impurity density in a semiconductor, are not directly related to the high frequency property of the Schottky diode.Rate this question:
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- 18.
Which of the below written statements is wrong for an integrated capacitor?
- A.
An integrated capacitor represents IC element consisting of conductive electrodes (plates), divided by isolation layer
- B.
In ICs the role of an integrated capacitor is often performed by reverse-biased p-n junctions of a transistor structure
- C.
The quality factor of an integrated capacitor is defined by the following: Q = 2 π f R Cwhere f −operating frequency, C − capacitance of a capacitor, R − resistance of a resistor sequentially connected with the transistor
- D.
The quality factor of an integrated capacitor characterizes loss of power at capacitive current junction
- E.
All the answers are correct
Correct Answer
C. The quality factor of an integrated capacitor is defined by the following: Q = 2 π f R Cwhere f −operating frequency, C − capacitance of a capacitor, R − resistance of a resistor sequentially connected with the transistorExplanation
The given statement is incorrect because the quality factor of an integrated capacitor does not depend on the resistance of a resistor sequentially connected with the transistor. The quality factor is solely determined by the operating frequency and the capacitance of the capacitor.Rate this question:
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- 19.
Which of the below mentioned statements is wrong for electronic lithography?
- A.
In this method the electron beams are used as a source of radiation
- B.
The method of electron beam lithography is based on non-thermal influence left by electron beam on resist
- C.
The ultraviolet beams fall on resist surface at electron beam lithography
- D.
It is possible to reduce diffraction effects by increasing the electron accelerating voltage in electron beam lithography
- E.
The correct answer is missing
Correct Answer
C. The ultraviolet beams fall on resist surface at electron beam lithographyExplanation
The given statement is wrong because ultraviolet beams are not used in electron beam lithography. In this method, electron beams are used as a source of radiation, not ultraviolet beams.Rate this question:
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- 20.
Which of the below mentioned statements is correct for a bipolar transistor in saturation mode?
- A.
Emitter and collector junctions are forward-biased
- B.
Emitter junction is forward-biased, and collector junction –reverse-biased
- C.
Transistor base resistance in this mode is maximum, as emitter and collector junctions inject large number of free particles to base region
- D.
Free carriers’ extraction takes place from transistor base being in this mode
- E.
The correct answer is missing
Correct Answer
A. Emitter and collector junctions are forward-biasedExplanation
In saturation mode, both the emitter and collector junctions of a bipolar transistor are forward-biased. This means that the emitter junction is forward-biased, allowing electrons to flow from the emitter to the base, and the collector junction is also forward-biased, allowing current to flow from the collector to the base. This configuration allows the transistor to operate in its maximum current-carrying capacity.Rate this question:
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