HW2-Due_Oct-11

# HW2-Due_Oct-11 - NNSE 618 Home assignment 2 Due 1 An...

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NNSE 618 Home assignment # 2 Due: October 11, 2011 1 An electron concentration in a GaAs sample at room temperature is 10 19 cm -3 . What is the position of the Fermi level with respect to the bottom of the conduction band? (The effective density of states in the conduction band of GaAs at room temperature is 4.7x10 17 cm -3 .). Higher? Lower? Why? (2 points). 2. The effective densities of states in the conduction and valence bands of GaAs at room temperature are 4.7x10 17 cm -3 and 7x10 18 cm -3 , respectively. How many electrons do you expect to find in a one millimeter cube of undoped GaAs at room temperature? How many holes? The energy gap of GaAs is 1.42 eV. (2 points). 3. What if the same (as in the problem 2) GaAs cube is doped with shallow donors with concentration 10 13 cm -3 . How many electrons do you expect to find now? How many holes? (3 points). 4. Two degenerate GaAs samples #1 and #2 have electron concentrations n 1 and n 2 such that n 2 / n 1 =8. The Fermi level in sample #1 is 40 meV above the bottom of the conduction band.

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HW2-Due_Oct-11 - NNSE 618 Home assignment 2 Due 1 An...

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