Physics for Electrical Engineers P r o f . B . J a l a l i E E 2 Homework #4 Due: Mar. 04 th , 2010 Assume: i) that n i in silicon at room temperature is equal to 10 10 cm-3 and ii) that N C = N V = 2.5 X10 19 cm-3 . 1. Consider an abrupt p-n junction with N A = 5 X 10 16 cm-3 and N D = 10 16 cm-3 . What is the excess minority carrier density at the edge of the space charge region in the two neutral regions of the p-n junction under a forward bias of 0.4 V? Take the value of the permittivity of silicon as 11.9 x 8.854 x 10-14 farads/cm. 2. Calculate the a) current due to i) electron injection and ii) hole injection and b) total current in the p-n junction in problem 1 under a forward bias of 0.4 V. Assume a wide base junction. Take the area of the junction to be 4 X 10-4 cm 2 . The minority carrier diffusion constants are 10 and 25 cm 2 /sec in the neutral n and p regions respectively. The minority carrier diffusion lengths are 10-3 and 10-2 cm in the neutral n and p regions respectively. 3.
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P-n junction, minority carrier, junction, Prof. B. Jalali