- 學位論文
高頻氮化鋁銦鎵/氮化鎵高電子遷移率電晶體之模擬分析與優化
Simulation analysis and optimization of high-frequency AlInGaN/GaN HEMTs
摘要
在本篇論文中，透過分析實驗已有的氮化鎵氮化鋁鎵之高電子遷移率電晶體的數據，提出優化的磊晶結構及元件表現。在分析實驗數據中，發現元件的二維電子氣濃度與短通道效應以及T型閘極的電容效應會限制元件的操作頻率。由於氮化鋁銦鎵作為元件能障層能產生較大的二維電子氣同時避免晶格不匹配，因此我們透過模擬不同氮化鋁銦鎵的組成，找出在晶格不匹配影響較小下能提供最高二維電子濃度的組成。而短通道效應的問題我們採用縮短元件通道的厚度以及氮化鋁鎵背屏障層來提升閘極對通道的控制。T型閘極的電容效應我們藉由改善T型閘極結構與鈍化層來降低。根據以上方法，我們提出了優化後的磊晶結構。 在結果中，透過模擬我們提出的磊晶結構，找出在閘極長度為60奈米時，元件能有最高𝑓𝑇，並討論接觸電阻與薄膜電阻的影響，以及分析不同介電系數的鈍化層在高頻元件的應用。最後，我們通過模擬評估元件能達到𝑓𝑇/𝑓𝑚𝑎𝑥為186/339 GHz在閘極長度為60奈米。
並列摘要
This paper proposes the optimized epitaxial structure and device performance by analyzing the experimental data of AlGaN/GaN high electron mobility transistors (HEMTs). In analyzing the experimental data, it is found that the two dimensional electron gas (2DEG) density, the short-channel effects of the device, and the capacitance effect of the T-type gate limit the operating frequency of the device. Since AlInGaN as a device energy barrier layer can generate more two-dimensional electron gas and avoid lattice mismatch. Therefore, by simulating different compositions of AlInGaN, we find the composition that provides the highest 2DEG with less effect of lattice mismatch. For the problem of the short channel effect, we use shrinking the thickness of the device channel and the AlGaN back barrier to improving the gate-to-channel control. The capacitance effect of the T-gate is reduced by improving the T-gate structure and passivation layer. According to the above methods, we propose an optimized epitaxial structure. In the results, by simulating our proposed epitaxial structure, it is found that the device can have the best 𝑓𝑇 when the gate length is 60 nm. The influence of contact resistance and sheet resistance is discussed. The passivation layer with different dielectric constants is analyzed for the application of high-frequency devices. Finally, we evaluate the device by the simulation to achieve 𝑓𝑇/𝑓𝑚𝑎𝑥 186/339 GHz at a gate length of 60 nm.