In this review the latest advances in the field of nanostructured photodetectors are considered, stating the types and materials, and highlighting the features of operation. Special attention is paid to the group-IV material photodetectors, including Ge, Si, Sn, and their solid solutions. Among the various designs, photodetectors with quantum wells, quantum dots, and quantum wires are highlighted. Such nanostructures have a number of unique properties, that made them striking to scientists’ attention and device applications. Since silicon is the dominating semiconductor material in the electronic industry over the past decades, and as germanium and tin nanostructures are very compatible with silicon, the combination of these factors makes them the promising candidate to use in future technologies.
Abstract-The instantaneous measurement of RF & microwave frequencies is widely used in electronic warfare (EW) for the determination of unknown signals over a broad frequency band. This paper presents an enhanced frequency measurement accuracy using three stages of novel RF frequency discriminator (FD) for RF front-end IFM Receivers. The appropriate structure of the designed frequency discriminator is implemented using a conventional PCB fabrication process. The frequency discriminator consists of two different hybrid layouts and one Wilkinson power divider, and all these components are implemented in microstrip technology, which is particularly important due to lower cost and easy integration into the PCB. To demonstrate the feasibility of the proposed structure, an RF-FE instantaneous frequency measurement (IFM) receiver has been realized based on 3-stage RF frequency discriminator. Simulation and measurement results have shown a frequency measurement accuracy less than 1 MHz (RMS) over the entire S-band.
In this article, the performance and design considerations of the planar structure of germanium on silicon avalanche photodiodes are presented. The dependences of the breakdown voltage, gain, bandwidth, responsivity, and quantum efficiency on the reverse bias voltage for different doping concentrations and thicknesses of the absorption and multiplication layers of germanium on the silicon avalanche photodiode were simulated and analyzed. The study revealed that the gain of the avalanche photodiode is directly proportional to the thickness of the multiplication layer. However, a thicker multiplication layer was also associated with a higher breakdown voltage. The bandwidth of the device, on the other hand, was inversely proportional to the product of the absorption layer thickness and the carrier transit time. A thinner absorption layer offers a higher bandwidth, but it may compromise responsivity and quantum efficiency. In this study, the dependence of the photodetectors’ operating characteristics on the doping concentration used for the multiplication and absorption layers is revealed for the first time.
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