Quiz 12 potential problems ChE 350 sp10

Quiz 12 potential problems ChE 350 sp10 - Sample question...

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Sample question for ChE 350 Spring 2010 Quiz 12 Name:________________________ 1 1. An example of a high brightness blue LED device is shown below [From Gee et al., “Flip- Chip Light Emitting Diode with Resonant Optical Microcavity,” US Patent 6,969,874 B1] The “MQW” layer is composed of In x Ga 1-x N. The band gap energies of GaN and InN are 3.44 eV and 1.89 eV, respectively. (a) It is desired that the LED will emit a blue color with a peak emission wavelength of 425 nm. What is the necessary In x Ga 1-x N composition to achieve this color? (b) Sketch the band structure of the device (GaN/In x Ga 1-x N/GaN) layers placing the p-side on the left of your diagram. You need to show the Fermi level and a reasonably accurate estimation of the relative band gaps of the layers, taking into consideration the answer provided in (a). [Note that the In x Ga 1-x N layer is the emitting “MQW” layer in the device.] (c) Sketch the band structure of a device with the MQW layer replaced with AlN (band gap energy is 6.2 eV). Would it still emit light?
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This note was uploaded on 12/13/2011 for the course CHE 350 taught by Professor Sanchez during the Spring '08 term at University of Texas at Austin.

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Quiz 12 potential problems ChE 350 sp10 - Sample question...

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