ece340Fall03HW8sol

# ece340Fall03HW8sol - ECE 340 Homework VIII Due Friday 16 3...

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ECE 340 Homework VIII Fall 2003 Due: Friday, October 10, 2003 1. An abrupt Si p-n junction has N a = 7x10 16 /cm 3 on the p-side and N d = 2x10 17 /cm 3 on the n-side. (a) Calculate the Fermi level positions at 300 K in the p and n regions. (b) Draw an equilibrium band diagram for the junction and determine the contact potential V o from the diagram. (c) Compare the results of part (b) with V o as calculated from Eq. (5-8). (d) Using Eq. (5-8), calculate and plot V o versus temperature ranging from 300 K to 500 K. Solutions: (a), At p side 16 10 71 0 ln 0.0259ln 0.398 1.5 10 iF i kT p E Ee V qn × −= = = × At n-side: 17 10 21 0 ln 0.0259ln 0.425 1.5 10 Fi i kT n E V × = = × (b), I found the easy way to draw this kind of energy band diagram is to draw the Fermi level first, then add the conduction band and valence band on p and n side according to the calculations, then connecting the two sides by curves. Therefore, 0 0.823 VV = (c), V 0 calculated from Eq. (5-8) is: 16 17 0 0 2 0 21 0 ln 0.0259ln 0.823 (1.5 10 ) ad i NN kT ×× × == = × Same as part (b) (d), Notice that the n i is also related to temperature through Eq. 3-26

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ece340Fall03HW8sol - ECE 340 Homework VIII Due Friday 16 3...

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