What happens when a semiconductor material is doped with a Group V element?
A Conductor
B N-type
C P-type
D Insulator
Doping a semiconductor with a Group V element (like phosphorus) introduces extra electrons, making the material an n-type semiconductor. These electrons are the majority charge carriers, enhancing the conductivity of the material.
What defines the conduction band in a semiconductor?
A Bound electrons
B Empty band
C Contains free electrons
D Full of electrons
The conduction band is the energy band in a semiconductor where electrons are free to move. These free electrons contribute to electrical conduction when they gain enough energy to overcome the band gap.
What happens when a p-type semiconductor is combined with an n-type semiconductor?
A Formation of p-n junction
B Increased resistance
C Magnetic field generation
D No reaction
When a p-type semiconductor is combined with an n-type semiconductor, a p-n junction is formed. This junction exhibits unique properties, such as rectification and the creation of a depletion region that prevents current flow in one direction.
What is the significance of the band gap in semiconductors?
A Determines voltage
B Determines resistance
C Determines conductivity
D Determines current
The band gap in a semiconductor determines its conductivity. A larger band gap means fewer free charge carriers, while a smaller band gap allows more electrons to jump into the conduction band, increasing conductivity.
What is the primary characteristic of a direct band gap semiconductor?
A High resistance
B Poor light emission
C Low current flow
D Efficient light emission
Direct band gap semiconductors (like Gallium Arsenide) efficiently emit light when an electron transitions from the conduction band to the valence band. This property makes them ideal for use in lasers and LEDs.
What happens to the carrier mobility in a semiconductor as temperature increases?
A Decreases
B Remains constant
C Becomes zero
D Increases
As temperature increases, carrier mobility in a semiconductor typically decreases. This occurs because increased thermal vibrations of the lattice impede the movement of charge carriers, reducing their mobility and overall conductivity.
What is the primary role of the depletion region in a p-n junction?
A Control voltage
B Generate light
C Block current flow
D Allow current flow
The depletion region in a p-n junction is where no charge carriers are present due to the recombination of electrons and holes. This region acts as a barrier that blocks current flow under reverse bias, making the diode function as a rectifier.
What is the effect of increasing the doping concentration in a semiconductor?
A Increases band gap
B Increases conductivity
C Decreases conductivity
D Increases resistance
Increasing the doping concentration in a semiconductor introduces more charge carriers, either electrons or holes, depending on the type of doping. This enhances the material’s electrical conductivity, making it more efficient for electronic devices.
What is the primary purpose of a photodetector?
A Detect light
B Amplify signals
C Emit light
D Regulate voltage
A photodetector is used to convert light into an electrical signal. It works by absorbing photons, which excite electrons, generating a current. This is essential in devices such as cameras and optical sensors.
What is the main characteristic of an intrinsic semiconductor?
A Light emission
B Free electrons
C No doping
D High conductivity
An intrinsic semiconductor is a pure semiconductor without any doping. The number of electrons in the conduction band is equal to the number of holes in the valence band. The material’s conductivity is solely dependent on temperature.
Which semiconductor material is commonly used for high-speed devices?
A Germanium
B Gallium Arsenide
C Silicon
D Copper
Gallium Arsenide (GaAs) is widely used for high-speed and high-frequency electronic devices due to its higher electron mobility compared to silicon. This makes it ideal for microwave, radar, and optical communication applications.
What is the principle behind the Hall effect?
A Current due to voltage
B Voltage due to current
C Voltage due to magnetic field
D Current due to magnetic field
The Hall effect occurs when a current-carrying conductor or semiconductor is exposed to a magnetic field, generating a transverse voltage (the Hall voltage) perpendicular to both the current and the magnetic field. This helps measure the magnetic field strength.
What is the primary role of a field-effect transistor (FET)?
A Switching
B Signal modulation
C Light detection
D Amplification
A Field-Effect Transistor (FET) primarily serves as a voltage-controlled switch. It controls current flow between the source and drain by applying a voltage to the gate terminal, making it widely used in digital and analog circuits.
What is the common application of a Zener diode?
A Amplification
B Light emission
C Signal modulation
D Voltage regulation
A Zener diode is designed to maintain a stable output voltage regardless of changes in the input voltage. It is used for voltage regulation in power supplies and voltage reference applications due to its breakdown voltage characteristic.
Which of the following affects the carrier concentration in a semiconductor?
A Temperature
B Light intensity
C Doping concentration
D All of the above
Carrier concentration in a semiconductor can be affected by several factors, including temperature (which influences thermal excitation of carriers), light intensity (which can generate electron-hole pairs), and doping concentration (which introduces additional charge carriers).