Simulation Study of HEMT performance for high frequency applications

Abstract

Due to its excellent material properties, GaN-based technology is set to become the dominant semiconductor in high-power and high-speed electronics. The research and development aimed at finding engineering solutions to gain the maximum potential from this material is gathering pace, and the work reported in this thesis is one of the many contributions to this goal. In this thesis, we have presented the results of the simulation of AlGaN/GaN HEMTs transistors and its performance for high frequency applications in order to manufacture high-performance components. In the first chapter, we recalled the physical and electronic properties of the GaN material. This analysis showed the fundamental differences between this material and more conventional III-V semiconductors such as gallium arsenide. Its large forbidden energy band, its large direct gap which is 3.4 eV, its high saturation speed as well as its piezoelectric aspects make it an ideal candidate for high power microwave applications. Unlike other large-gap semiconductors such as silicon carbide or diamond, gallium nitride offers the possibility of producing ternary alloys such as AlGaN, InGaN or AlInN, which makes it possible to produce heterojunctions with high electronic mobility that can be used. for manufacturing faster field effect transistors. These properties allow HEMTs transistors to present better frequency performance. In the second chapter, we have introduced the High Electron Mobility Transistors (HEMTs). Then, we studied the operating principle of the HEMT transistor based on AlGaN/GaN, its structure and the different layers that compose it and the different substrates choice such as Silicon Carbide Substrates (SiC), Sapphire Substrates (Al2O3) and Silicon Substrates (Si). The HEMTs on AlGaN/GaN heterostructure on sapphire substrate have shown desirable performances but due to poor thermal conductivity of sapphire substrate they are not suitable for high temperature and high power application. The suitability of AlGaN/GaN HEMTs on silicon substrates have been proved by RoundHEMT device. In the third chapter, we modeled our device which is the HEMT AlGaN/GaN, we simulated and interpreted the different results. For this, we used the simulation software: MATLAB. We simulate the electrical characteristics of AlxGa1-xN/GaN nanostructures HEMTs by using samples with a different gate bias, different gate width, and with different thickness of AlxGa1-xN barrier layer 57 and spacer layer, the study of the influence of the various geometrical parameters of the transistor on the electrical characteristics in order to obtain a structure conducive to good operation. At the final point, our simulation results shows that the device designs of AlxGa1-xN/GaN nanostructures HEMTs could be proposed for ultra-high speed logic amplifications of nextgeneration and high power switching applications fields in the future.