氮化鋁鎵/氮化鎵高電子遷移率電晶體（HEMT）具有高崩潰電場，高電子遷移率和高電子密度，因此在高功率下具有出色的性能。目前由於P型氮化鋁鎵/氮化鎵高電子遷移率電晶體的製程可靠度較其他方式來得穩定，以至於成為目前常關型HEMT的主流結構，不過其仍有許多可靠度議題需要被研究。
本論文以元件導通條件進行長時間的開態偏壓以及變溫量測，進一步去觀察元件的特性變化，而發現在變溫狀態下，元件各項特性會呈現衰減的趨勢，則與升溫後電子的能量變化相關導致此現象。
在變溫量測的實驗中，我們發現元件特性在升溫時有劣化的趨勢，而我們初步推測原因為晶格散射以及缺陷捕捉電子的現象產生，隨後我們透過公式進行了萃取活化能的計算，得到0.18eV及0.15eV，代表了缺陷在材料中的位置，分別在AlGaN barrier及GaN buffer當中，進一步可以確認前面所述的推論是否正確。
另外在長時間的偏壓條件下，我們分別使用閘極偏壓為5V及6V及7V進行量測，發現元件的臨界電壓會有正偏及負偏的現象，由此現象透過能帶圖及結構圖得以去分析元件有電子捕獲及電洞注入的機制，在5V時，臨界電壓的正偏移與與缺陷捕捉電子有關，而在偏壓超過6V之後，臨界電壓的負偏移與電洞的注入有關，而注入的電洞與電子隨著時間增加進行複合導致產生後續正偏移的現象。

AlGaN/GaN High Electron Mobility Transistor (HEMT) devices deliver excellent performance in high power applications owing to their wide bandgap, high electron mobility, and high electron sheet density.
Despite the reliability issues still under investigation, the p-GaN gate HEMT is still the only commercially normally-off GaN-based device for power applications owing to its relatively stable fabrication.
In this thesis, we measured p-GaN devices under long-term on state stress and reliability testing of thermal stress to further understand performance degradation and bidirectional threshold voltage shift.
In the case of thermal stress, we inferred that lattice scattering and electron trapping were related to performance degradation after measurement. Moreover, we extracted the average activation energy of 0.18eV and 0.15eV which indicated the trap location in AlGaN barrier layer and GaN buffer layer.
In the case of long term on state stress, we obtained bidirectional threshold voltage shift under gate bias of 5V, 6V, 7V. We used a band diagram and a schematic structure to analyze the mechanisms of electron trapping and hole injection. The reasonable explanation for bidirectional threshold voltage shift can be described as hole injection induced negative VTH shift and injected holes recombined with electrons in the channel, resulting in slightly positive VTH shift.

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