Answer Happy

Exercise 8.1 (25 points) (Si pin photodiode speed) Consider a Si pin photodiode that has a player of thickness 0.75 um and a i-Si layer of width 10 um. It is reverse biased with a voltage of 110 V and for Si the relative permittivity is er = 11. The internal speed of this type of detector is determined by: (i) the drift time of the charge carriers across the i- layer after the electron-hole pair is formed due to light absorption; and (ii) the diffusion of electrons across the player into the junction region to restore charge neutrality. Drift velocity (m) 10 Electron . 104 Hole 103 102 104 10 10 107 Electric field (V-In (a) What is the speed of the response based on the absorption in the i-Si layer? (b) What is the speed of the response based on the diffusion across the player? (Note: the diffusion constant for Si is De = 3 x 104 m”/s) (c) Based on your calculation at points (a) and (b) which of the factors above is the most limiting factor in the response speed of this pin photodiode?