ece340Spring04hw6sol - ECE 340 1. Homework VI Due:...

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ECE 340 Homework VI Spring 2004 Due: Wednesday, February 18, 2004 (30 points total) 1. (a) A Si bar 0.1 cm long and 100 μm 2 in cross-sectional area is doped with 5x10 16 /cm 3 arsenic atoms. Find the current at 300 K with 10 V applied. Repeat for a similar Si bar 1 μm long. (b) Upon a steady illumination uniform excess carriers are generated in the Si bar. Assume that τ n = p = 1 μs for the excitation. Determine the percentage of increase in current in part (a) assuming an optical generation rate, g op =10 21 EHP/cm 3 -s is obtained. Solutions: (a) As: donor, n type. Lookup graph, 2 830 / n cm Vs µ = 2 280 / p cm Vs = Electric field: / Vd = . For 0.1 cm long Si bar, drift current: () 62 1 9 1 6 3 2 4 10 1.6 10 5 10 830 / (10 / 0.1 ) 6.64 10 np n n V IA q n p A q n A q n d cm C cm cm Vs V cm A µµ −− =+ = × × ×× × For 1 μm long Si bar, electrical field 5 /1 0 / 1 1 0 / V m Vc m == = . From Fig 3-24, the electron drift velocity is saturated at thermal velocity of about 10 7 cm/s.
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ece340Spring04hw6sol - ECE 340 1. Homework VI Due:...

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