Question

7. Laser light is incident on a 2 mm3 cube of semiconductor which produces electrons by photoionization uniformly within the cube at a steady rate of 5 x 1018 electrons/s-cm3. Assuming no charge is lost within the cube (i.e. no recombination), calculate the current out of one of the faces of the cube.

Answer 1

Given Total volume of cube = 2 mm^3 = 2 times 10^- 9 m^3 e^- production rate is given = 5 times 10^10 e^-/sec cm^3 means from 1 cm^3 (volume) e^- produced = 5 times 10^10 e^-/s e^- produced from total volume Rightarrow Rightarrow from 1 cm^3 rightarrow 5 times 10^10 e^- foe 1 m^3 rightarrow 5 times 10^10 times 10^6 times 2 times 10^- 9 e^- = 10 times 10^15 e^- e^- produced from one face of the cube (in 1 second) = 10 times 10^15/6 = 1.1667 times 10^15 e^- current out of one face (in 1 second) i = dq/dt = Delta q/Delta t = 1.1667 times 10^15/1 1 = 1.1667 times 10^15 Ampere