ece340Spring04HW9Sol

# ece340Spring04HW9Sol - ECE 340 Homework IX Due Wednesday...

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ECE 340 Homework IX Spring 2004 Due: Wednesday, March 03, 2004 1. An abrupt Si p-n junction is formed by alloying a uniformly doped n-type silicon bar where N d = 8x10 16 /cm 3 in the beginning. During the alloying process, a uniform counter doping of acceptors of N a = 1.4x10 17 /cm 3 is introduced in the region for x<0. Basically, x<0 is the p-side and x>0 is 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 250 K to 500 K. Solutions: (a), At x<0, 16 3 61 0 pad p NN c m =−= × In p region, 16 10 0 ln 0.0259 ln 0.394 1.5 10 ip Fp i kT p E Ee V qn × −= = × = × In n region, 16 10 81 0 ln 0.0259 ln 0.401 1.5 10 Fn in i kT n E V × = × = × (b), V 0 = 0.795 V (c), Equations 5-8: 16 16 0 22 0 81 0 0.0259ln 0.0259ln 0.795 ad ii VV nn ×× × == = Result is same as (b) (d), Notice that the n i is related to temperature through Eq. 3-26 Method 1: Read n i from Figure 3-17, plug into Eqn 5-8 to obtain the plot.

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ece340Spring04HW9Sol - ECE 340 Homework IX Due Wednesday...

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