Quiz 10 potential problems ChE 350 sp10

Quiz 10 potential problems ChE 350 sp10 - o C). 4. A...

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Sample question for ChE 350 Spring 2010 Quiz 10 Name:________________________ 1 1. A silicon sample is doped with 10 19 B atoms/cm 3 . The intrinsic free electron concentration in Si at room temperature is 3 10 10 5 . 1 × cm , the band gap energy is 1.1 eV, and recall that kT at room temperature is 0.026 eV. The effective density of states of Si, N C ,is 3 19 cm 10 2 . 3 × . (A) What is the equilibrium electron concentration n at 300K? (B) Sketch qualitatively the Fermi level in the band gap for this Si sample at 300K. (C) What is the equilibrium hole concentration p at 1000K? 2. A piece of silicon doped with boron has a resistivity of 100 Ω cm at room temperature. (A) If the hole mobility is sec V cm 550 2 0 = μ , what is the dopant concentration? (Show your work) (B) Sketch qualitatively the Fermi level with respect to the conduction and valence band energies. 3. (A) Draw the band diagram for a p-n junction at room temperature. (B) Draw the band diagram for the same p-n junction at high temperature (>1000
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Unformatted text preview: o C). 4. A silicon sample is doped with 10 17 As atoms/cm 3 . The intrinsic free electron concentration in Si at room temperature is 3 10 10 5 . 1 cm . (A) What is the equilibrium hole concentration p at 300K? (B) Sketch the position of the Fermi level in the band gap. 4. Below, the intrinsic electrical conductivity of a semiconductor at two temperatures is tabulated: [Useful relations: h e e p e n + = ; ( ) kT E N n g c 2 exp = ; 1 kT =26 meV at 298K]. ( a ) Determine the band gap energy (in eV) for this material. Answer: _____________________ ( b ) Estimate the electrical conductivity at 298 K. Answer:______________________ Sample question for ChE 350 Spring 2010 Quiz 10 Name:________________________ 2 (c) In the band diagram shown below, sketch the Fermi level position for this semiconductor. (D) Sketch qualitatively the Fermi level in the band gap for this Si sample at 1000K....
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Quiz 10 potential problems ChE 350 sp10 - o C). 4. A...

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