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Leya [2.2K]
3 years ago
5

(a) If 5 x 10^17 phosphorus atoms per cm3 are add to silicon as a substitutional impurity, determine the percentage of silicon a

toms per unit volume that are displaced in the single crystal lattice.
(b) Repeat part (a) for 2 x 10^15 boron atoms per cm3 added to silicon.
Engineering
1 answer:
Y_Kistochka [10]3 years ago
7 0

Answer:

The percentage of silicon atoms per unit volume that are displaced in the single crystal lattice = 0.001 %

The percentage of silicon atoms per unit volume that are displaced in the single crystal lattice with boron atoms = 0.4 ×10^{-5} %

Explanation:

No. of phosphorus atoms = 5 × 10^{17} \ cm^{-3}

The volume occupied by a single Si atom

V_{si} = \frac{a^{3} }{8}

V_{si} = \frac{5.43^{3}(10^{-8} )^{3}  }{8}

V_{si} = 2 × 10^{-23} \frac{cm^{3} }{atom}

n_{si} = \frac{1}{V_{si} }

n_{si} = 5 × 10^{22} \frac{atoms}{cm^{3} }

PCT = \frac{N_p}{N_{si}}   100

Put the values in above equation we get

PCT = \frac{5 (10^{17} )}{5 (10^{22}) } 100

PCT = 10^{-3} = 0.001 %

These are the percentage of silicon atoms per unit volume that are displaced in the single crystal lattice.

(b).

No. of boron atoms = 2 × 10^{15} \ cm^{-3}

The volume occupied by a single Si atom

V_{si} = \frac{a^{3} }{8}

V_{si} = \frac{5.43^{3}(10^{-8} )^{3}  }{8}

V_{si} = 2 × 10^{-23} \frac{cm^{3} }{atom}

n_{si} = \frac{1}{V_{si} }

n_{si} = 5 × 10^{22} \frac{atoms}{cm^{3} }

PCT = \frac{N_p}{N_{si}}   100

Put the values in above equation we get

PCT = \frac{2 (10^{15} )}{5 (10^{22}) } 100

PCT = 0.4 ×10^{-5} %

These are the percentage of silicon atoms per unit volume that are displaced in the single crystal lattice.

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