EE138 Final Fall 2009

EE138 Final Fall 2009 - Name Date EE 138 Fall Exam Fall...

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Unformatted text preview: Name: Date: EE 138 Fall Exam Fall 2009 Total time allowed: 180 minutes Total points: 100 points One-side of one 8.5” by 11” sheet of notes allowed. NOTE: The questions are NOT weighted equally. Please use your time wisely. ___________________________________________________________________________ Problem #1: (15 total points) Below are schematic band diagrams for several materials. Answer the following questions and include your reasoning. (a) Which are likely to be semiconductors? (2 pts) (b) Which are direct bandgap semiconductors? (2 pts) Name: Date: (c) Which are insulators? (2 pts) (d) Which has the highest electron mobility? (3 pts) (e) Which has the lowest hole mass? (2 pts) (f) Which would you use for a visible LED? (2 pts) (g) Which is most likely the hardest? (2 pts) Name: Date: Problem #2 : (10 total points) The intensity (energy density) of infrared light with a frequency of 5 x 10 12 Hz decays by a factor of 100 in traveling through 1 micron of a conductor with a Hall coefficient of 2.01 x 10-9 m 3 /C. Calculate the electron mobility, assuming the material to be nonmagnetic. Name: Date: Problem #3: (15 total points) Consider the following conduction band profile created in a semiconductor material: (a) Taking the conduction band edge as E = 0 for the electron coming from the left, what k and is needed so that the electron energy will be greater than the first barrier? (5 pts) (b) If the electron has energy 0.1 eV in Region I, and d is thin enough that the electron may tunnel, what is k in Region II? (5 pts) (c) For the electron to get from Region I to V, a quantum well level must be at the correct energy to allow the...
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EE138 Final Fall 2009 - Name Date EE 138 Fall Exam Fall...

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