20111ee2_1_2011_EE2_HW3 - 2 a What is the range of bandgap...

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Physics for Electrical Engineers P r o f . B . J a l a l i E E 2 Homework #3 Due: Feb 3, 2011, 4:00pm You may or may not find the following information useful: h=6.626 × 10 -34 J-s Mass of the electron=9.1 × 10 -31 kg Bandgap of Silicon at T=300 K: E g =1.12 eV n i (for Si at room temperature T=300 K) = 1X10 10 cm -3 N C (for Si at room temperature T=300 K) = 2.8X10 19 cm -3 N V (for Si at room temperature T=300 K) = 1.04X10 19 cm -3 1. a) What is the emission wavelength of a Si LED? b) Is Si a good choice for LED and why? c) How can you exploit the uncertainty principle to your advantage? (Hint: Uncertainty principle may help resolve certain limitation on Si as LED material)
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Unformatted text preview: 2. a) What is the range of bandgap energy you need to have to create a white LED? b) If that range of bandgap energy is not available, how else can you create a white LED? (Hint: The problem requires you to search online.) 3. Explain why Si doped with 10 14 cm-3 Sb is n-type at 400 K but similar doped Ge is not. 4. A Si sample is doped with 8 X 10 16 cm-3 donors and 2 X 10 16 cm-3 acceptors. Find the position of the Fermi level with respect to E i at 300 K. 5. What is the probability that an electron state with energy 0.12 eV above the Fermi energy will be occupied at T= 0K, 200K, and 400K?...
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This note was uploaded on 10/07/2011 for the course EE 2 taught by Professor Vis during the Spring '07 term at UCLA.

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