Design and Analysis of High Frequency Solar Blind Photodetectors for Communication with Red Signal

Abstract

Advantages associated with high-speed communication and data security bolsters the eligibility of Free Space Optical (FSO) and Visible Light Communication (VLC). In this context, characteristics like low noise equivalent power, high frequency response associated with the photodetectors play pivotal roles in determining the performance of the entire communication FSO/RF link. In this study, the authors present the design of detector sensitive to red signal coming from commercial laser with wavelength 650nm (photon energy 1.9eV), while being blind to the rest of sun spectrum. High-sensitivity to signal of commercial laser is provided by double barrier tunnelling p-i-n photodiode made up of AlxGa1-xAs heterostructure with mildly doped p-type and n-type regions. The photodetector operates as window discriminator. The quantum operation of double barrier tunnelling significantly narrows the band of detectable red light. In addition, all photons with high energy are effectively cut off by p-i-n filter, positioned at the top of the structure. This filtering layer works at the same time as a solar cell and provides reverse bias to the photodetector. Low noise equivalent power on the order of 0.2pW/√?? and cut-off frequency of 20GHz make this device eligible for FSO communication.