Laser light is incident on a 1 mm3 cube of semiconductor whi

Laser light is incident on a 1 mm^3 cube of semiconductor which produces electrons by photoionization uniformly within the cube at a steady rate of 4.5 Times 10^18 electrons/s-cm^3. Assuming no charge is lost within the cube (i.e. no recombination), calculate the current out of one of the faces of the cube.

Solution

Volume of the cube of semiconductor V = 1 mm ³

                                                          = (10 ^-1 cm) ³

                                                          = 10 ^-3 cm ³

Production rate of electrons = 4.5 x10 ¹⁸ electrons /s -cm ³

So, No.of electrons producted from 1 mm³ cube is N per second = Production rate x volume of the cube

                                                                          = (4.5 x10 ¹⁸) (10 ^-3 )

                                                                          = 4.5 x10 ¹⁵

Charge of N electrons q = (4.5 x10 ¹⁵ ) Charge of electron

                                   = (4.5 x10 ¹⁵ ) (1.6 x10 ^-19 )

                                  = 7.2 x10 ^-4 C

Therefore current out of one of the faces of the cube i = q / t

Where t = time = 1 s

So, i = (7.2 x10^-4 C ) / 1s

        = 7.2 x10 ^-4 A

       = 0.72 x10 ^-3 A

       = 0.72 mA