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(10 points) Consider a strip of silicon that has a rectangular cross-section wit

ID: 1584450 • Letter: #

Question

(10 points) Consider a strip of silicon that has a rectangular cross-section with dimensions 3.00 mm by 150 m, and through which there is a uniform current of 50mA. The silicon strip is a semi-conductor that has been doped with a controlled phosphorus impurity. The doping has the effect of greatly increasing n, the number of charge carriers per unit volume, as compared with the value for pure silicon. In this case, n 1.5 x 10 23 m. (a) What is the current density in the strip? (b) What is the drift speed in the strip? 6.

Explanation / Answer

area, A=3*10^-3*150*10^-6 = 450*10^-9 m^2

current, I=50*10^-3 A


n=1.5*10^23 m^-3

a)


current density, J=I/A


=(50*10^-3)/(450*10^-9)


=1.11*10^5 A/m^2

b)


drift speed, Vd=J/n*e


Vd=1.11*10^5/(1.5*10^23*1.6*10^-19)


Vd=4.625 m/sec