Practice free Semiconductor Electronics: Materials, Devices and Simple Circuits (Physics) NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
The potential difference developed across the p-n junction at equilibrium, which opposes further flow of carriers, is often called:
The NCERT states, 'Since this potential tends to prevent the movement of electron from the n region into the p region, it is often called a barrier potential.'
Why is it not possible to form a p-n junction by simply joining a p-type semiconductor slab with an n-type semiconductor slab physically?
From Example 14.3, 'No! Any slab, howsoever flat, will have roughness much larger than the inter -atomic crystal spacing (~2 to 3 Ã…) and hence continuous contact at the atomic level will not be possible. The junction will behave as a discontinuity for the flowing charge carriers.'
What constitutes the 'depletion layer' in a p-n junction?
Under 'POINTS TO PONDER', point 12 mentions, 'When such a junction is made, a ‘depletion layer’ is formed consisting of immobile ion-cores devoid of their electrons or holes. This is responsible for a junction potential barrier.'
What is the typical order of thickness of the depletion region in a p-n junction?
The NCERT text states, 'The thickness of depletion region is of the order of one-tenth of a micrometre.'
The primary cause for the flow of charge carriers in the drift current during p-n junction formation is:
The text explains, 'Due to this field, an electron on p-side of the junction moves to n-side and a hole on n-side of the junction moves to p-side. The motion of charge carriers due to the electric field is called drift.'
What is the polarity of the potential established across a p-n junction at equilibrium?
The NCERT states, 'The n-material has lost electrons, and p material has acquired electrons. The n material is thus positive relative to the p material.'
Which of the following statements correctly describes the formation of energy bands in a solid?
According to the context, 'when the atoms come together to form a solid they are close to each other. So the outer orbits of electrons from neighbouring atoms would come very close or could even overlap. This would make the nature of electron motion in a solid very different from that in an isolated atom. ... Because of this, each electron will have a different energy level. These different energy levels with continuous energy variation form what are called energy bands.'
In a material where the conduction band is partially filled and the valence band is partially empty, or where the conduction and valence bands overlap, what is the expected electrical conductivity?
The context states: 'One can have a metal either when the conduction band is partially filled and the balanced band is partially empty or when the conduction and valance bands overlap. When there is overlap electrons from valence band can easily move into the conduction band. This situation makes a large number of electrons available for electrical conduction. ... Therefore, the resistance of such materials is low or the conductivity is high.'
What is the typical energy band gap ($E_g$) for an insulator?
The text explicitly states for insulators, 'a large band gap $E_g$ exists ($E_g > 3 \text{ eV}$). There are no electrons in the conduction band, and therefore no electrical conduction is possible.'
Which statement is true regarding the energy band structure of elemental semiconductors at 0 K?
Figure 14.1 description notes: 'The lower band, called the valence band, consists of closely spaced completely filled energy states.' Also, earlier text mentions 'With no external energy, all the valence electrons will reside in the valence band.'
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