Gallium has three valence electrons and arsenic has five valence electrons. These two are combined to form gallium arsenide.
12. Gallium arsenide is a
A. binary semiconductor
B. trinary semiconductor
C. ternary semiconductor
D. unary semiconductor
Answer: A
Gallium arsenide is a binary semiconductor and high temperatures should be avoided which might result in dissociation of the surface.
13. Addition of impurities is essential for creating switching devices.
A. true
B. false
Answer: A
It is necessary to introduce impurities into the semi-insulating GaAs to facilitate the creation of switching devices.
14. The behavior of the switching element is decided by
A. selection of impurity
B. concentration density
C. selection of impurity & concentration density
D. none of the mentioned
Answer: C
The selection of the impurity and its concentration density determines the behavior of the switching element.
15. ______ elements can act as either donors or acceptors.
A. group II
B. group III
C. group IV
D. group V
Answer: C
Group IV elements such as silicon can act as either donor (on Ga sites) or as acceptors (on As sites).
16. Which element is smaller?
A. arsenic
B. gallium
C. silicon
D. aluminum
Answer: A
Arsenic is smaller than gallium and silicon. The covalent radius of Ga is 1.26 Armstrong unit whereas for As is 1.18 Armstrong unit.
17. ______ is used as the dopant for the formation of n-type material.
A. aluminum
B. arsenic
C. silicon
D. gallium
Answer: C
Group IV impurities tend to occupy gallium sites. Silicon is used as the dopant for the formation of n-type material.
18. Increase in positive charge ___________ the effective nuclear charge.
A. increases
B. decreases
C. exponentially increases
D. does not affect
Answer: A
An increase in the positive charge of the nucleus results in an increase in the effective nuclear charge thereby increasing the effective atomic radius.
19. ___________ is used for the formation of p-type material.
A. beryllium
B. magnesium
C. beryllium and magnesium
D. aluminum
Answer: C
Group II elements such as beryllium and magnesium can be used for the formation of p-type materials.
20. Which is the lightest p-type dopant?
A. beryllium
B. magnesium
C. silicon
D. arsenic
Answer: A
Beryllium is the lightest p-type dopant for GaAs, deep implantation of the dopant atoms can be accomplished with less lattice damage.
