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

If the energy of a photon of sodium light $(λ = 589 n m)$ equals the band gap of a semiconductor, calculate the minimum energy required to create hole-electron pair. Take, $h = 6 .6 \times 10^{- 34} Js, c = 3 \times 10^{8} m / s$

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 3

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

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

MEDIUM

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

If the energy of a photon of sodium light (λ=589 nm) equals the band gap of a semiconductor, calculate the minimum energy required to create hole-electron pair. Take, h = 6.6×10-34 Js, c = 3×108 m/s

Important Questions on Semiconductor Devices and Digital Circuits

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If the energy of a photon of sodium light $(λ = 589 n m)$ equals the band gap of a semiconductor, calculate the minimum energy required to create hole-electron pair. Take, $h = 6 .6 \times 10^{- 34} Js, c = 3 \times 10^{8} m / s$