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

EASY

12th CBSE

IMPORTANT

Earn 100

The band gap of an alloy semiconductor gallium arsenide phosphide is $1.98 e V .$ Calculate the wavelength of radiation that is emitted when electrons and holes in this material combine directly. What is the colour of the emitted radiation? Take $h = 6.6 \times 10^{- 34} J s, c = 3 \times 10^{8} m / s$

Important Questions on Semiconductor Devices and Digital Circuits

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

Pure silicon at

300 K

has equal electron and hole concentrations of

1.5 \times 10^{16} m^{- 3} .

Doping by indium increases the hole concentration to

4.5 \times 10^{22} m^{- 3} .

Calculate the new electron concentration in the doped silicon.

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

Mobilities of electrons and holes in a sample of intrinsic germanium at room temperature are

0.54 m^{2} v^{- 1} s^{- 1}

and

0.18 m^{2} v^{- 1} s^{- 1}

respectively. If the electron and hole densities are equal to

3.6 \times 10^{19} m^{- 3}

, calculate the germanium conductivity. Take,

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

MEDIUM

12th CBSE

IMPORTANT

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

A semiconductor has the electron concentration of

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

and hole concentration of

4 \times 10^{13} c m^{- 3} .

Is the semiconductor p-type or n-type? Also, calculate the resistivity of this semiconductor. Given electron mobility

= 24,000 c m^{2} V^{- 1} s^{- 1}

and hole mobility

= 200 c m^{2} V^{- 1} s^{- 1}

MEDIUM

12th CBSE

IMPORTANT

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

A semiconductor has the electron concentration

4 \times 10^{12} c m^{- 3}

and the hole concentration

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

. Is the substance n-type or p-type? Also, calculate the conductivity of this semiconductor. Given electron mobility

= 22,000 c m^{2} V^{- 1} s^{- 1}

and hole mobility

= 150 c m V^{- 1} s^{- 1} .

Take,

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

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

Determine the number density of donor atoms which have to be added to an intrinsic germanium to produce an n-type semiconductor of conductivity

0.06 S m^{- 1} .

Given the mobility of electrons

= 0.39 m^{2} V^{- 1} s^{- 1} .

Neglect the contribution of holes to the conductivity. Take:

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

HARD

12th CBSE

IMPORTANT

PHYSICS A Reference Book for Class 12 Volume 2>Chapter 6 - Semiconductor Devices and Digital Circuits>Problems For Practice>Q 5

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} .

MEDIUM

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

MEDIUM

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

The band gap of an alloy semiconductor gallium arsenide phosphide is 1.98 eV. Calculate the wavelength of radiation that is emitted when electrons and holes in this material combine directly. What is the colour of the emitted radiation? Take h=6.6×10-34Js, c = 3×108 m/s

Important Questions on Semiconductor Devices and Digital Circuits

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