Simulation Study of Threshold Voltage of Normally Off AlGaN/GaN MOS-HEMTs
| Autor: | Weng, Ke-Li, 翁可力 |
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| Rok vydání: | 2015 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 104 AlGaN/GaN high electron mobility transistor (HEMT) is extensive investigation in recent years, because of their superior material properties that suitable for high frequency and high power applications. However, the conventional structure of AlGaN/GaN HEMT whose threshold voltage is operated in the negative voltage that also called depletion mode (normally on); moreover, it is not convenient for circuit design and fail-safe operation. Therefore, Enhancement-mode (normally off) is the wild of many research teams studied. In addition to, the framework of devices is scale down accompanied with the non-ideal effects. It cannot be ignored, and especially carriers confinement in channel under the gate oxide. It is called the tunneling effect (quantum tunneling) Therefore, in this thesis work a physical simulation of AlGaN/GaN MOS-HEMT is developed using commercially available software ATLAS from SILVACO Int. Based on drift - diffusion carrier transport equations. The quantum tunneling model (density gradient model) calibrate to the experimental data so that it approaches actual device situation and reliability. In this thesis, a comprehensive study of approaches to achieve positive threshold voltage. We have investigated the influence of recess gate, gate oxides, gate metallization on the devices characteristics. In this study, it’s found that TiO2 (Titanium dioxide) as a gate oxide layer exhibits better transfer and output I-V curve compared to the gate recessed MOS-HEMTs with Al2O3 (aluminum oxide). The maximum transconductance of 259mS/mm, an off-state breakdown voltage of 650V, and a small drain leakage current (≈10-9 mA/mm). Furthermore, the Pt (platinum) substitute for Ni (nickel) as metal gate that threshold voltage can be increased to 1.3V. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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