This set of VLSI Multiple Choice Questions & Answers (MCQs) focuses on “MESFET”.
1. The gallium arsenide field effect transistor is ________ majority carrier device.
a) bulk current insulation
b) bulk current conduction
c) bulk voltage insulation
d) bulk voltage conduction
Explanation: The gallium arsenide field effect transistor is a bulk current-conduction majority carrier device and is fabricated from bulk gallium arsenide.
2. Method used for fabrication of GaAs FET is
a) ion implantation
Explanation: The methods used for fabrication of gallium arsenide field effect transistors are high-resolution photolithography and ion implantation.
3. How many masking stages does fabrication of GaAs FET require?
Explanation: The fabrication of GaAs field effect transistor requires six to eight masking stages and processing is relatively simple.
4. Which region is heavily doped?
Explanation: In GaAs FET, a narrow metal Schottky barrier gate separates the more heavily doped drain and source.
5. Which MOSFET contains Schottky diode?
Explanation: GaAs MOSFET differs from silicon MOSFET due to the presence of Schottky diode to separate two thin n-type regions.
6. D type and E type MESFETs operates by ________ of existing doped channel.
c) e type MESFET
d) d type MESFET
Explanation: D type and E type MESFETs, that is ON and OFF devices operates by the depletion of an existing doped channel.
7. Which is ON device?
a) e type MESFET
b) d type MESFET
Explanation: D-MESFET is normally ‘ON’ and its threshold voltage is negative and E-MESFET is ‘OFF’ and its threshold voltage is positive.
8. The threshold voltage cannot be determined using
a) concentration density
b) channel thickness
c) implanted impurity
d) channel depth
Explanation: The threshold voltage can be determined using concentration density, channel thickness and implanted impurity but cannot be determined using channel depth.
9. A highly doped thick channel exhibits _______ threshold voltage.
a) smaller negative
b) smaller positive
c) larger negative
d) larger positive
Explanation: A highly doped thick channel exhibits a large negative threshold voltage. By reducing channel thickness and concentration density, positive threshold in E-MESFET can be fabricated.
10. The MESFET has maximum
a) gate to drain voltage
b) gate to source voltage
c) source voltage
d) drain voltage
Explanation: The MESFET has a maximum gate to source voltage Vgs of about 0.7-0.8 volt owing to the diode action of schottky diode gate.
11. Schottky barrier is created due to the difference in
c) work function
Explanation: Schottky barrier is an electrostatic potential barrier created at the interface as a result of the difference in work function of the two materials.
12. As the separation between metal-semiconductor surface is reduced, induction charge
c) remains constant
d) is not affected
Explanation: As the separation between metal-semiconductor surface is reduced, induction charge in the semiconductor increases and also the space charge layer widens.
13. In MESFET for gate _____ junction is used.
a) pnp junction
b) npn junction
c) schottky junction
d) n junction
Explanation: Metal semiconductor field effect transistor is similar to JFET. In this instead of using pn junction for gate, Schottky gate is used.
14. MESFET is constructed in
d) All of the mentioned
Explanation: MESFET is constructed in compound semiconductor technologies lacking high quality surface such as GaAs, InP and SiC.
Sanfoundry Global Education & Learning Series – VLSI.
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