In GaAs FET, a narrow metal Schottky barrier gate separates the more heavily doped drain and source.
82. Which MOSFET contains Schottky diode?
A. GaAs
B. Ga
C. Si
D. SiO2
Answer: A
GaAs MOSFET differs from silicon MOSFET due to the presence of a Schottky diode to separate two thin n-type regions.
83. D type and E type MESFETs operates by ________ of the existing doped channel.
A. depletion
B. enhancement
C. e type MESFET
D. d type MESFET
Answer: A
D type and E type MESFETs, that is ON and OFF devices operate by the depletion of an existing doped channel.
84. Which Transistor is the ON device?
A. e type MESFET
B. d type MESFET
C. depletion
D. enhancement
Answer: B
D-MESFET is normally ‘ON’ and its threshold voltage is negative and E-MESFET is ‘OFF’ and its threshold voltage is positive.
85. The threshold voltage cannot be determined using
A. concentration density
B. channel thickness
C. implanted impurity
D. channel depth
Answer: D
The threshold voltage can be determined using concentration density, channel thickness, and implanted impurity but cannot be determined using channel depth.
86. A highly doped thick channel exhibits _______ threshold voltage.
A. smaller negative
B. smaller positive
C. larger negative
D. larger positive
Answer: C
A highly doped thick channel exhibits a large negative threshold voltage. By reducing channel thickness and concentration density, the positive threshold in E-MESFET can be fabricated.
87. The MESFET has maximum
A. gate to drain voltage
B. gate to source voltage
C. source voltage
D. drain voltage
Answer: B
The MESFET has a maximum gate to source voltage Vgs of about 0.7-0.8 volt owing to the diode action of the Schottky diode gate.
88. Schottky barrier is created due to the difference in
A. voltages
B. thickness
C. work function
D. density
Answer: C
The Schottky barrier is an electrostatic potential barrier created at the interface as a result of the difference in the work function of the two materials.
89. As the separation between metal-semiconductor surface is reduced, induction charge
A. increases
B. decreases
C. remains constant
D. is not affected
Answer: A
As the separation between metal-semiconductor surfaces is reduced, the induction charge in the semiconductor increases, and also the space charge layer widens.
90. In MESFET for gate _____ junction is used.
A. PNP junction
B. NPN junction
C. Schottky junction
D. n junction
Answer: C
The metal-semiconductor field-effect transistor is similar to JFET. In this instead of using the PN junction for the gate, the Schottky gate is used.
91. MESFET is constructed in
A. SiC
B. InP
C. GaAs
D. All of the mentioned
Answer: D
MESFET is constructed in compound semiconductor technologies lacking high-quality surfaces such as GaAs, InP, and SiC.
92. Gallium arsenide crystals are grown from
A. boron oxide
B. silicon oxide
C. silicon nitride
D. boron nitride
Answer: D
The growth of gallium arsenide crystals from high purity boron nitride cubicles is becoming the primary growth technique.
93. Wafers in GaAs fabrication are thermally unstable.
A. true
B. false
Answer: B
The fabrication of GaAs includes the production of round wafers and they are thermally stable and have superior semi-insulating properties.
94. The sequence of the steps followed in the fabrication of GaAs is
A. lapping
B. polishing
C. grinding
D.All of the above
Answer: D
The steps followed in the fabrication of GaAs are grinding the As-grown boules, wafering, edge rounding, lapping, polishing, and then wafer scrubbing.
95. Which devices are fabricated using a planar process?
A. enhancement mode MESFET
B. depletion mode MESFET
C. enhancement mode MOSFET
D. depletion-mode MOSFET
Answer: B
The depletion-mode devices are fabricated using a planar process where n-type dopants are directly implanted into semi-insulating GaAs.
96. Threshold voltage can be varied by
A. varying impurity concentration
B. varying doping level
C. varying channel length
D. varying source voltage
Answer: B
Threshold voltage in GaAs can be varied by varying the channel thickness and the doping level of the active region.
97. Stable native oxide was produced by
A. oxidation of silicon
B. oxidation of gallium
C. oxidation of boron
D. oxidation of aluminum
Answer: A
The driving force of silicon technology was brought about as the result of the presence of stable native oxide which was readily produced through the oxidation of silicon.
98. In GaAs technology, deposited dielectric films bring about
A. passivation
B. combination
C. decomposition
D. diffusion
Answer: A
In GaAs technology, due to the absence of a stable native oxide deposited dielectric films bring about passivation or encapsulation.
99. Formation of the n-active layer is achieved by
A. indirect ion implantation
B. direct ion implantation
C. liquifying
D. wafering
Answer: B
The formation of the n-active layer is achieved by direct ion implantation into the GaAs semi-insulating substrate through the insulating layer.
100. Implantation of ________ is done for the formation of source and drain.
A. n- layer
B. n+ layer
C. p- layer
D. p+ layer
Answer: B
Implantation of a deep low resistivity n+ layer is done for the formation of source and drain and n-layer for the formation of the channel layer.
