Semiconductor Electronics: Materials, Devices and Simple Circuits MCQs for NEET — Physics Questions with Answers

Carbon (C) is an insulator because the energy required to excite an electron from the valence band to the conduction band is much higher in carbon than in silicon (Si) or germanium (Ge). This means that fewer electrons are available for conduction in carbon compared to silicon and germanium.

Out of 5 valence electrons of phosphorous, 4 are shared with Si. Fifth electron can be approximated to revolve around nucleus. Situation is like H-atom $ En \approx -13.6 /n^2 ev $ for n = 1 , EN = -13.6 ev $E inside lattice = { En \over \epsilon_1^2 } = { -13.6 \over 12^2} =0.1 ev $

A P-type semiconductor is created by doping an intrinsic semiconductor with a trivalent impurity (such as boron). This leads to the creation of 'holes' which can accept electrons. However, the overall charge of the P-type semiconductor remains neutral because the number of positively charged holes is balanced by the number of negatively charged electrons.

Strong overlapping of different atomic orbitals in a solid leads to the formation of energy bands. These energy bands are crucial in determining the electrical properties of materials, such as whether they behave as conductors, semiconductors, or insulators.

An intrinsic semiconductor has a finite resistance that decreases with temperature. As temperature increases, more electron-hole pairs are generated, thereby increasing the number of charge carriers and decreasing the resistance.

The behavior of germanium (Ge) as a semiconductor is due to the width of the forbidden band being small and narrow. In semiconductors, the forbidden band (also called the band gap) is small enough to allow electrons to jump from the valence band to the conduction band at room temperature, thus allowing the material to conduct electricity.

The advantage of a PN junction diode over a tube valve that is not true is 'Unlimited life'. While PN junction diodes do have many advantages such as no warming-up time, large efficiency, and low power consumption, they do not have an unlimited lifespan. They can degrade over time due to factors such as heat and electrical stress.

$ \beta = { \alpha \over 1 -\alpha } $