Estudo Numérico Comparativo de Desempenho de Dispositivos Baseados em Grafeno para Aplicações em Optoeletrônica

Abstract

In this work, we performed a numerical investigation of modeling and optimization of several devices for optoelectronic applications in which the graphene was used in order to improve the performance of the device. In the first part, a numerical investigation has been performed on the limits of miniaturization for a graphene-assisted modulator considering two different configurations, in both cases the critical coupling condition representing the OFF state, and the transmission level of -3 dB the ON state. In addition, the power consumption per bit of 100 fJ/bit was established as the cutoff parameter for both modulator configurations, as well as the minimum insertion loss for the ON state of 0.4 eV for the hybrid modulator. Considering the parameters aforementioned, our results showed that both configurations of modulators have great potential of miniaturization, high modulation speed and low power consumption. This work, therefore, provides a theoretical framework for the fabrication of graphene-based modulators in its optimal configuration, in terms of minimum energy consumption per bit (33.57 and 100.07 fJ/bit), as well as wide modulation bandwidth (285.53 and 131.9 Ghz), for which we have the smallest dimension (8.89 and 10.05µm2) that allows maintaining a satisfactory efficiency in terms of extinction ratio and energy expenditure. The second part consisted of a comparative numerical analysis between photodiodes which operates in the UV domain using Silicon Carbide (4H-SiC) in the active layer, of Metal-Semiconductor-Metal (MSM) configuration. For performance comparison purposes, graphene and nickel were used separately as electrode materials. The analysis consisted of comparing the performance of the photodetector (measured as a function of the current photo, dark current and signal to noise ratio) for different variations of physical and geometric properties for the two types of electrode materials, in order to verify the advantages and drawbacks for each material, and also to set the optimal configuration for each one. The results have shown that using graphene as an electrode layer can improve the photodetector performance in comparison to nickel, especially in terms of photocurrent, without the penalty of an increasing in dark current, which makes it possible to use this material as a promising technology to replace the traditional metallic electrodes, whose opacity to light is a great issue to overcome, especially for the MSM configuration, once it reduces the performance threshold. Furthermore, the optimize version of both structures obtained in this work has also a great importance in order to help fabrication process, which the main goal is to find the best configuration as possible.