I am putting the 2nd part of HW#1 in a separate post because it involves a different topic. These problems, on energy scales, are not difficult I think. If you start on them right away it will get you thinking about things that will help you get more out of our upcoming classes on the nature of semiconductors. Energy scales play a big role in that.
#5. a) Roughly, what is "room temperature" in Kelvin? b) What is KT, in eV, where K is Boltmann's constant and T is room temperature?
#6. What is the band gap of Si, Ge and of diamond in eV?
#7. What is exp{E/KT} at room temperature if E is 1 eV?, 0.5 eV?
#8. What is the wavelength and energy, in eV, of a photon of red light and of green or blue light?
#9. a) If you substitute one phosphorus atom for a Si atom in silicon, what is the energy of the localized bound state that forms in the neighbor of the P atom?
b) What about for Au doped into Ge?(optional)
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What happened to hw problems 3 and 4? Part I has questions 1 and 2, and then we skip to 5 in Part II.
ReplyDeletetrue, there is no 3 or 4. part I starts at 1, part II starts at 5. 3 and 4 are a "buffer", just in case...
ReplyDeleteDoes anyone have any ideas for problem 9?
ReplyDeleteLouis Steele:
ReplyDelete5a) $T\approx295K$ \\
5b) $kT=(8.617\times10^{-5}eV/K)(295K)=25meV$ \\\\
6. Si energy gap $\approx1.1$eV at room temperature \\
Ge energy gap $\approx0.7eV$ at room temperature \\
Diamond energy gap $\approx5.5eV$ at room temperature \\\\
7. What is $e^{E/kT}$ at room temperature if E is 1 eV?, 0.5 eV? \\
$e^{1eV/0.025eV}=2.35\times10^{17}$ \\
$e^{0.5eV/0.025eV}=4.85\times10^{8}$ \\\\
8. What is the wavelength and energy, in eV, of a photon of red light and of green or blue light? \\
Red: $620nm<\lambda<750nm -> E=hc/\lambda\to 1.7eV<E<2eV$ \\
Green: $495nm<\lambda<570nm\to 2.2eV<E<2.5eV$ \\
Blue: $450nm<\lambda<495nm\to 2.5eV<E<2.8eV$ \\\\