Design of Solar Blind Photodetectors for Communication with Green Signal (λ= 0.532µm) in Space....

Very high-speed data transmission is possible with Free Space Optical (FSO) communication and high-speed Visible Light Communication (VLC). It is preferred for communication between satellites and ground stations, under-water communication, and other applications due to its favourable characteristics, such as high frequency and wider bandwidths that can allow transmission speeds of the order of 100Gb/s, which are correlated with the visible region of the electromagnetic spectrum. However, limitations associated with the propagating media's spectral absorption characteristics have stymied further advancement of such technologies. The basic elements of a long-distance optical communication system are commercial lasers that operate in red, green, and blue light, as well as three photodetectors that are each sensitive to specific wavelengths (colours). The current research (Part II) shows the design and operation of a solar-blind photodetector that can operate with a green wavelength of 532nm. Design and Results of the Study: The solar-blind photodetector is made up of two sections: a filter and a double barrier tunnelling diode made of InxGa1-xN (Indium Gallium Nitride) heterostructure (where x denotes the mole fraction). The topmost, approximately 1m thick section serves as a filter and a p-i-n solar cell, providing the photodiode with the requisite voltage bias. All photons with wavelengths shorter than 532nm are absorbed by the filter with Eg (Energy Band Gap)=2.33eV. The lower section contains a double barrier tunnelling photodiode that operates at Eg=2.28eV. It consists of a 2.5nm wide n-type lightly doped quantum well sandwiched between two lightly doped quantum wells Barriers with a thickness of 10nm. The photodiode's 0.12m top and bottom regions are doped with p and n (2105cm-3) form impurities, respectively. The device's illuminated cross-section area has been set to 1mm2.

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