21. The energy is greater as the closer the electron is to the nucleus.
A. true
B. false
Answer: A
The closer the electron is to the nucleus the greater is the holding influence of the nucleus and the greater is the energy required for the electron to break loose and become free.
22. Which are more stronger?
A. outer orbit electrons
B. outer orbit protons
C. inner orbit electrons
D. inner orbit protons
Answer: A
Outer orbit electrons are said to be stronger than inner orbit electrons because of their ability to break loose from the parent atom. These are called valence electrons.
23. Gallium arsenide is made up of
A. single element
B. compound of two elements
C. compound of three elements
D. compound of four elements
Answer: B
Gallium arsenide is a compound semiconductor that is defined as a compound of two elements whereas silicon is a single element semiconductor.
24. Gallium has ______ valence electrons.
A. two
B. three
C. four
D. five
Answer: B
Gallium has three valence electrons and arsenic has five valence electrons. These two are combined to form gallium arsenide.
25. 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.
26. 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.
27. The behaviour 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.
28. ______ 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).
29. 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.
30. ______ 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.
