EE119 Discussion Section 9 (04/05/10) Professor: Jeff Bokor TA: Xi Luo 1. Photodiode – review on p-n junction, depletion region, bias; charge carrier transport – diffusion and drift; pn photodiode vs. pin photodiode For a particular PIN photodiode, a pulse of light containing 5 × 10 12 incident photons at wavelength of 1.55 μ m gives rise to, on average, 1.5 × 10 12 electrons collected at the terminals of the device. (a) What is the energy incident to the photodiode? What is the quantum efficiency of the photodiode? (b)The diffusion length is 0.5mm in this detector. If the electron diffusion velocity is 7 × 10 6 cm/s, estimate the response time of the detector. (Do not take drift into account.) (c) The thickness of the intrinsic layer in the photodiode is typically about 2.5mm. If the drift velocity of the electrons in this region is 10 7 cm/s, estimate the response time of the detector. (Do not take diffusion into account). 2.
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Liquid crystal, 0.5mm, nematic liquid crystal, Jeff Bokor