Determine the conductivity and resistivity of pure germanium at 300 K , assuming that at this temperature the concentration of germanium is 2.5 × 10 13 c m - 3 The electron and hole mobilities are 3600 c m 2 V - 1 s - 1 and 1700 c m 2 V - 1 s - 1 , respectively. Take, 1 .6 × 10 - 19 C .

Given: The concentration of Ge atoms, n i = 2.5 × 10 13 cm - 3 The mobility of electron, μ e = 3600 c m 2 V - 1 s - 1 The mobility of holes, μ h = 1700 c m 2 V - 1 s - 1 Say, the electron and hole concentrations are n e and n h respectively. Since, it is pure germanium, n e = n h = n i = 2.5 × 10 13 c m - 3 The conductivity of doped germanium, σ = e n e μ e + n h μ h = e n i μ e + μ h = 1.6 × 10 - 19 × 2.5 × 10 13 3600 + 1700 = 0.0 212 S c m - 1 = 2.12 S m - 1 The resistivity, ρ = 1 σ = 1 2.12 = 0.472 Ω m

When the voltage drop across a p - n junction diode is increased from 0.70 V to 0.71 V , the change in the diode current is 10 m A . What is the dynamic resistance of the diode?

Given, Dynamic resistance is defined for devices whose resistance is not constant with voltage or current. The change in voltage is, ∆ V = 0.71 - 0.70 = 0.01 V The change in the diode current, Δ I = 10 m A We know the dynamic resistance, r d = ∆ V ∆ I = 0 .01 V 10 × 10 - 3 = 1 Ω

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12th CBSE

IMPORTANT

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Germanium is doped one part per million with indium at room temperature. Calculate the conductivity of doped germanium. Given, concentration of $G e$ atoms $= 4.4 \times 10^{28} m^{- 3},$ intrinsic carrier concentration $(n_{i}) = 2.4 \times 10^{19} m^{- 3},$ $μ_{e} = 0.39 m^{2} V^{- 1} s^{- 1}$ and $μ_{h} = 0.19 m^{2} V^{1} s^{- 1} .$

Important Questions on Semiconductor Devices and Digital Circuits

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12th CBSE

IMPORTANT

PHYSICS A Reference Book for Class 12 Volume 2>Chapter 6 - Semiconductor Devices and Digital Circuits>Problems For Practice>Q 6

Determine the conductivity and resistivity of pure germanium at

300 K,

assuming that at this temperature the concentration of germanium is

2.5 \times 10^{13} c m^{- 3}

The electron and hole mobilities are

3600 c m^{2} V^{- 1} s^{- 1}

and

1700 c m^{2} V^{- 1} s^{- 1},

respectively. Take,

1 .6 \times 10^{- 19} C

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12th CBSE

IMPORTANT

PHYSICS A Reference Book for Class 12 Volume 2>Chapter 6 - Semiconductor Devices and Digital Circuits>Problems For Practice>Q 7

The resistivity of pure germanium at a particular temperature is

0.52 Ω m .

If the material is doped with

10^{20}

atoms per

m^{- 3}

of a trivalent impurity material, determine the new resistivity. The electron and hole mobilities are given to be

0.2 m^{2} V^{- 1} s^{- 1}

and

0.4 m^{2} V^{- 1} s^{- 1}

respectively. Take

e = 1.6 \times 10^{- 19} C

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12th CBSE

IMPORTANT

PHYSICS A Reference Book for Class 12 Volume 2>Chapter 6 - Semiconductor Devices and Digital Circuits>Problems For Practice>Q 8

A sample of germanium is doped to the extent of

10^{14}

donor atoms per cm³ and

7 \times 10^{13}

acceptor atoms per

{c m}^{3}

. The resistivity of pure germanium at the temperature of the sample is

60 Ω c m .

Find the total conduction current density due to an applied electric field of

2 V c m^{- 1} .

The electron and hole mobilities are given to be

3800 c m^{2} V^{- 1} s^{- 1}

and

1800 c m^{2} V^{- 1} s^{- 1},

respectively. Take,

e = 1.6 \times 10^{- 19} C

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12th CBSE

IMPORTANT

PHYSICS A Reference Book for Class 12 Volume 2>Chapter 6 - Semiconductor Devices and Digital Circuits>Problems For Practice>Q 9

The energy gap in germanium is

0.75 e V .

Compare the intrinsic conductivity of germanium at

300 K

and

330 K

. Take

k_{B} = 8.6 \times 10^{- 5} e V K^{- 1} .

EASY

12th CBSE

IMPORTANT

PHYSICS A Reference Book for Class 12 Volume 2>Chapter 6 - Semiconductor Devices and Digital Circuits>Problems For Practice>Q 1

When the voltage drop across a

p

n

junction diode is increased from

0.70 V

0.71 V,

the change in the diode current is

10 m A .

What is the dynamic resistance of the diode?

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12th CBSE

IMPORTANT

PHYSICS A Reference Book for Class 12 Volume 2>Chapter 6 - Semiconductor Devices and Digital Circuits>Problems For Practice>Q 2

The $V-I$ characteristic of a silicon diode is as shown in figure. Calculate the resistance of the diode at

(i) $I = 15 m A$ and

(ii) $V = - 10 V$

Question Image

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12th CBSE

IMPORTANT

PHYSICS A Reference Book for Class 12 Volume 2>Chapter 6 - Semiconductor Devices and Digital Circuits>Problems For Practice>Q 3

p

n

junction is designed to withstand currents up to a maximum of

10 m A .

A resistance of

200 Ω

is connected in series with it. When forward biased, the diode has a potential drop of

0.5 V

which is assumed to be independent of current. Find the maximum voltage of the battery to forward bias the diode.

EASY

12th CBSE

IMPORTANT

PHYSICS A Reference Book for Class 12 Volume 2>Chapter 6 - Semiconductor Devices and Digital Circuits>Problems For Practice>Q 4

The silicon diode shown in figure is rated for a maximum current of $100 m A .$ Calculate the minimum value of resistor $R$ . Assume the forward voltage drop across the diode to be $0.7 V$ .
Question Image

Germanium is doped one part per million with indium at room temperature. Calculate the conductivity of doped germanium. Given, concentration of Ge atoms =4.4×1028 m-3, intrinsic carrier concentration (ni)=2.4×1019 m-3, μe=0.39 m2V-1s-1 and μh=0.19 m2V1s-1.

Important Questions on Semiconductor Devices and Digital Circuits

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