Select one of the optoelectronic devices and explain how it operates. Please inc

Question

Select one of the optoelectronic devices and explain how it operates. Please include drawings to aid in the explanation. A silicon p^+ -n junction doped such that the hole concentration in the n-type material is 5 astir 10^6 cm^-3 on the n side and a cross sectional area of 10^-2 cm^2. If tau_p = 0.2 mu sec and D_p = 40 cm^2/sec, calculate the current with a forward bias of 0.4V at T = 300K. If the material (e.g., silicon) that makes up an LED is doped with additional donor and acceptor atoms, would the wavelength of the light increase, decrease, or remain the same. Explain why.

Explanation / Answer

A photodiode is a semiconductor device that converts light into current. The current is generated when photons are absorbed in the photodiode. A small amount of current is also produced when no light is present. Photodiodes may contain optical filters, built-in lenses, and may have large or small surface areas. Photodiodes usually have a slower response time as their surface area increases. The common, traditional solar cell used to generate electric solar power is a large area photodiode.

Photodiodes are similar to regular semiconductor diodes except that they may be either exposed (to detect vacuum UV or X-rays) or packaged with a window or optical fiber connection to allow light to reach the sensitive part of the device. Many diodes designed for use specifically as a photodiode use a PIN junction rather than a p–n junction, to increase the speed of response. A photodiode is designed to operate in reverse bias.

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