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Solid State Physics: Structure and Properties of Materials

M.A. Wahab

Chapter 13

Semiconducting Properties of Materials - all with Video Answers

Educators

Chapter Questions

29:19

Problem 1

What is intrinsic semiconductor? Obtain an expression for the intrinsic carrier concentration in an 1 intrinsic semiconductor. Under what condition will the Fermi level be in the middle of the forbidden gap?

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20:11

Problem 2

What are intrinsic and extrinsic semiconductors? Discuss the location of the Fermi levels under suitable limiting conditions and give the necessary theory.

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25:29

Problem 3

Derive an expression relating the shift in the Fermi level and the carnier density in an intrinsic semiconductat.

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08:57

Problem 4

Why does the conductivity of a semiconductor change with impurity content? Compare this with the behaviour of metallic conductor.

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24:44

Problem 5

Explain the Hall effect. Derive an expression for the Hall coefficient of semiconductor on two band model carriers.

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07:10

Problem 6

Find the fraction of electrons excited into conduction band in germanium at 1001K. $300 \mathrm{~K}$ and $1200 \mathrm{~K}$.

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04:47

Problem 7

In an intrinsic semiconductor, the effective mass of the electron is $0.07 \mathrm{~m}_{\mathrm{l}}$ and that of hole is $0.4 \mathrm{~m}_{0 \text { - }}$ where $m_{0}$ is the rest mass of the electron. Calculate the intrinsic concentration of charge carriens at 300 $\mathrm{K}$. Given: the energy gap $=0.7 \mathrm{eV}$.

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06:40

Problem 8

A sample of germanium whose intrinsic carrier cono 1715
material by adding acceptor atoms at a rate of one atom per $4 \times 10^{8}$ germanium atoms. The density of germanium atom is $4.4 \times 10^{28} / \mathrm{m}^{3}$. Compare the density of clectrons with intrinsic charge camiers. Assume that all the acceptor atoms are ionized at $300 \mathrm{~K}$.

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03:15

Problem 9

The intrinsic carrier concentration $$
\text { of a germanium sample }
$$
is $2.4 \times 10^{14} / \mathrm{m}^{3}$ at $300 \mathrm{~K}$. Its electron and hole mobilities are $0.39$ and $0.19$ $\mathrm{m}^{2} \mathrm{~V}^{-1} \mathrm{~s}^{-1}$ respectively. Calculate the conductivity of the sample.

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06:19

Problem 10

Calculate the current produced in a small germanium plate of area $1 \mathrm{~cm}^{2}$ and of thickness $03 \mathrm{~mm}$, when
a potential difference of 2 volts is apphed across its faces. The intrinsic carrier concentration of geranium is $2 \times 10^{19} / \mathrm{m}^{3}$ and the mobilities of electron and holes are $0.36$ and $0.17 \mathrm{~m}^{2} \mathrm{~V}^{-1} \mathrm{~s}^{-1}$, respectively.

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06:59

Problem 11

Compare the densities of charge carriers in a pure silicon crystal at the two temperatures $300 \mathrm{~K}$ and 330 Ans. 0.14. $\mathrm{K}$. The energy gap for silicon is $1.1 \mathrm{eV}$.

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04:12

Problem 12

Consider a sample of $n$ -type silicon with $\mathrm{N}_{\mathrm{D}}=10^{21} / \mathrm{m}^{\prime}$. Determine the electron and hole densities al 300 $\mathrm{K}$. The intrinsic carrier concentration for silicon at $300 \mathrm{~K}$. is $9.8 \times 10^{17} \mathrm{~m}$

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13:52

Problem 13

If a sample of silicon is doped with $3 \times 10^{23}$ arsenic atoms and $5 \times 10^{23}$ atoms of boron, determine electron and hole concentrations if the intrinsic charge carriers of silicon are $2 \times 10^{16} / \mathrm{m}^{3}$

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04:54

Problem 14

Deicrmine the demsity of the donor atoms which have to he added to intrinsie germanium to make it ar
wmiconductor is $0.125 \mathrm{~m}^{2} \mathrm{~V}^{-4} \mathrm{~s}^{-1}$

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03:27

Problem 15

An electric field of $100 \mathrm{~V} / \mathrm{m}$ is applied to a sample of n-type semiconductor whose Hall coefficient is $0.0125 \mathrm{~m}^{1} \mathrm{C}$. Determine the current density in the sample, assuming the electron mobility to be $0.36$ Ans. $2880 \mathrm{~A} / \mathrm{m}^{2} \mathrm{f}$
$m^{2} v^{-1} x^{-1}$

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06:50

Problem 16

eurrent flowa through a simple $p$ -n juncrion diode at room temperature when is is reverse biased with $0.15 \mathrm{~V}$. Determine the amount of current which will flow when it is forward-bianed with the sams voltage. Ans. $1.04 \mathrm{~m} \mathrm{~A}_{1}$

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