Explain the very large generation rate obtained in the first part of problem 1. How many electron-hole pairs are created by an electron passing through a layer of 1μm thick at the scattering limited velocity?
Problem 1
How many electron-hole pairs are generated per second in Si by interband impact generation at x1 If E(x1)...3x105V/cm. If N(x1)=n1=1.0x1010cm-3, what is the number of electron-hole pairs generated per unit volume per second? How does this compare with the optical generation rate obtained In problem 2? (Use Figure 2).
Problem 2
Si, GaAs and CdS crystals are exposed to a yellow light of wavelength 5500A and intensity 1012 photons/cm2-sec. Verify that the photon energy Is 2.25eV. How many electron-hole pairs are generated per unit volume per second in each crystal? Assume that crystal is very thin and the light is absorbed uniformly in the very thin slice. Why do we need to assume the crystal to be very thin? (Use λ-1.24/E and Figure 2.) (Partial answer: Si, 7x1015cm-3s-1.)
