GATE 2017 EC Solved question paper

[GATE-2018]

Download GATE 2017 EC- Electronics & Communication Engineering Questions and Detailed Solution of Session-1 examination from the link below. All questions are properly solved like the one below.

Qn
A bar of Gallium Arsenide (GaAs) is doped with Silicon such that the Silicon atoms
occupy Gallium and Arsenic sites in the GaAs crystal. Which one of the following
statement is true?


(a) Silicon atoms act as p-type dopants in Arsenic sites and n-type dopants in
Gallium sites.


(b) Silicon atoms act as n-type dopants in Arsenic sites and p-type dopants in
Gallium sites.

© Silicon atoms act as p-type dopants in Arsenic as well as Gallium sites.

(d) Silicon atoms act as n-type dopants in Arsenic as well as Gallium sites


Solution (a)
When GaAs is doped with Silicon, the two possibilities arise

(i) Silicon  can replace  Gallium
(ii) Silicon  can replace  Arsenic So,  if  the  Silicon  replaces  Gallium  then Silicon has one more electron. So, the extra electron  is available  for  conduction.  It  will make  it  n-type.

One the other hand, Silicon replaces Arsenic it has  one less electron  and it will  make it p-type.

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