?Which one of the following statement(s) is false A substitution impurity in donor and acceptor atoms does not cause any disturbances in the crystal lattice of semiconducting material. In an n-type semiconductor, the free electrons concentration approximately equals the density of donor atoms Each donor atom contributes two free electrons to semiconducting crystal lattice. Mobility of charge carriers equals its average speed v divided by the applied electric field E.

Exercises 1. A silicon p-n junction has the hole and electron resistivity are 0.001 .m, 0.004 .m respectively in T-250 °K. The intrinsic carrier density is 6.2×10¹0 m³, the electron and hole diffusion length are 1.8×104 m, 1.1×104 m respectively, and th=8 µs. Find reverse saturation current density. 2. Given a Si diode with the following physical ch/s the doping concentration in the p-type is 2.25×10¹7 cm³ and in the n-type is 2.25×10¹4 cm³, junction area is 2×10³ cm², life time of hole in n-region=10 µs, life time of electron in p-region =50 µs, hole and electron mobilities are 600 cm³V's¹ and 2100 cm²V¹s¹ respectively, the intrinsic carrier concentration is 1.4x100 cm³ and the voltage is 0.66 v operation at room temperature. Calculate Jp(0) and Jn(0) then calculate the total diode current. 3. A silicon p-n junction has energy of C.B. and V.B. are 0.9 eV, 0.1 eV respectively at 200 K. the hole and electron mobility, resistivity are 0.16 m²/V.s, 0.36 m²/V.s, 0.0025 92.m and 0.005 2.m.…

A. Why does the conductivity of a semiconductor and some insulators change with impurity content? Compare this with the behaviour of metallic conductors. B. Discuss the location of the Fermi levels of intrinsic and extrinsic (n-type and p-type) semiconductors in low temperature and high temperature ranges. C. Discuss why the structure of the p-n junction is so important to modern technologies that impact our daily life.

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