For all parts of this question, assume that all the incident radiation onto the semiconductor surface...

 

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For all parts of this question, assume that all the incident radiation onto the semiconductor surface is transmitted into the semiconductor medium without loss (due to reflection). (a) If d is the thickness of the photodetector material, I, is the intensity of the incoming radiation, show that the number of photons absorbed per unit volume of sample is To (1-e-ad), dhv nph where a is the absorption coefficient of the material. (b) What is the thickness of a Ge crystal and an Ino.53Ga0.47As crystal layer that is needed for absorbing 90% of the incident radiation at 1.5m? The absorption coefficient at 1.5 m wavelength is 5105 m for Ge and 7105 m for Ino.53ga0.47As crystal. (c) Suppose that each absorbed photon liberates one electron hole pair in a photodetector with unity quantum efficiency (n = 100%) and that the photogenerated electrons are immediately collected. Thus, the rate of charge collection is limited by the rate of photon generation. What is the external photocurrent density for the photodetectors in (b) if the incident radiation is 100W/mm? For all parts of this question, assume that all the incident radiation onto the semiconductor surface is transmitted into the semiconductor medium without loss (due to reflection). (a) If d is the thickness of the photodetector material, I, is the intensity of the incoming radiation, show that the number of photons absorbed per unit volume of sample is To (1-e-ad), dhv nph where a is the absorption coefficient of the material. (b) What is the thickness of a Ge crystal and an Ino.53Ga0.47As crystal layer that is needed for absorbing 90% of the incident radiation at 1.5m? The absorption coefficient at 1.5 m wavelength is 5105 m for Ge and 7105 m for Ino.53ga0.47As crystal. (c) Suppose that each absorbed photon liberates one electron hole pair in a photodetector with unity quantum efficiency (n = 100%) and that the photogenerated electrons are immediately collected. Thus, the rate of charge collection is limited by the rate of photon generation. What is the external photocurrent density for the photodetectors in (b) if the incident radiation is 100W/mm?