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Electronics and Communication Engineering - Electromagnetic Field Theory

Exercise : Electromagnetic Field Theory - Section 4
46.
Consider the following statements: The function of oxide layer in an IC device is to
  1. mask against diffusion or non implant
  2. insulate the surface electrically
  3. increase the melting point of silicon
  4. produce a chemically stable protective layer
Of these statements:
1, 2, 3 are correct
1, 3, 4 are correct
2, 3, 4 are correct
1, 2, 4 are correct
Answer: Option
Explanation:

Oxide layer cannot have any effect on melting point of silicon. Moreover before melting silicon breaks down.

47.
An extrinsic semiconductor sample has 6 billion silicon atoms and 3 million pentavalent impurity atoms. The number of electrons and holes is
3 million each
6 billion each
3 million free electrons and very small number of holes
3 million holes and very small number of free electrons
Answer: Option
Explanation:

When pentavalent impurity is added, the number of fresh electrons is very large as compared to number of holes.

48.
In a reverse biased p-n junction, the reverse bias is 4V. The junction capacitance is about
0.1 F
4 μF
10 nF
20 pF
Answer: Option
Explanation:
No answer description is available. Let's discuss.
49.
Photoconductive devices uses
metallic conductors
good quality insulators
semiconductors
either (a) or (c)
Answer: Option
Explanation:
No answer description is available. Let's discuss.
50.

Assertion (A): Oxide coated cathodes are very commonly used.

Reason (R): Work function of oxide coated cathode is 1 eV whereas it is 4.5 eV for pure tungsten.

Both A and R are true and R is correct explanation of A
Both A and R are true but R is not a correct explanation of A
A is true but R is false
A is false but R is true
Answer: Option
Explanation:

Lower work function leads to higher emission current. Therefore oxide coated cathodes are commonly used.

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