氮化鎵高電子遷移率電晶體暫態電流特性 與電流散射之研究

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題名:	氮化鎵高電子遷移率電晶體暫態電流特性與電流散射之研究
作者:	卓志偉;Cho, Chih-Wei
貢獻者:	電機工程學系
關鍵詞:	氮化鎵;暫態電流;電流散射
日期:	2023-10-30
上傳時間:	2024-03-05 17:51:56 (UTC+8)
出版者:	國立中央大學
摘要:	氮化鎵高電子遷移率電晶體(GaN HEMT)其材料具有高電子遷移率、高崩潰電場、高飽和速度等特性，特別適用於 5G 基地台、低軌道衛星等這些需要高功率輸出的應用。然而，氮化鎵於磊晶過程產生的缺陷會在高電流、高電壓操作下引起可靠度相關的問題。電流散射效應會造成汲極輸出電流降低，這會嚴重影響元件模型的準確度並且限制元件的輸出功率。本文以商用穩懋氮化鎵元件進行暫態電流量測分析，元件分別施加不同的應力關閉電壓到導通電壓觀察電流暫態的變化，導通電壓又可分成線性區和飽和區做比較。當元件從關閉狀態切換至開啟狀態線性區時，觀察到與溫度相關的熱激發載子逃脫效應，陷阱活化能大約為 EA= 0.5 eV。相反的，當元件從關閉狀態切換至開啟狀態飽和區時，較不易觀察到與溫度相關的載子逃脫現象。推測可能原因是汲極和源極間存在較高的電場，使得更容易導致電場輔助穿隧效應現象發生。此外，本文也提出藉由脈衝小訊號 S 參數量測方式，元件經由應力關閉電壓後隨即以短脈衝開啟電壓來測量 S 參數，觀察元件發生電流散射時小訊號參數的變化，利用等效電路建立模型並萃取出小訊號參數。可以觀察到在元件關閉時，高的汲極偏壓會導致汲極與源極間的電阻(Rds)、閘極與汲極間電容(Cgd)、汲極與源極間的電容(Cds)等元件本質參數有明顯的變化。元件受到關閉狀態高電場作用之下，通道電子可能被 AlGaN 能障層、緩衝層內的缺陷捕獲造成。 ;GaN Nitride material has many superior properties, such as high electron mobility, high critical electric field, and high saturation velocity. It is especially suitable for 5G base stations and low-orbit satellites requiring high-output power. However, defects generated in the epitaxial crystallization process of gallium nitride could cause reliability issues under high-current and high-voltage operations. The current dispersion effect will cause the drain output current to decrease, which will seriously affect the accuracy of the device modeling and limit the device’s output power. In this study, the commercial WIN gallium nitride device is adopted to investigate the change of current transient. Applying different off-state stress and on-state voltage to observe the changes in current transient. The on-state voltage can be divided into linear and saturation regions to compare. When the device switches from the off-state to the on-state linear region, the temperature dependence of the de-trapping is observed, and it is thermally activated with trap activation energy around EA=0.5 eV. On the contrary, temperature-dependent de trapping is hard to observe when the device switches from the off-state to the on-state saturation region. It is speculated that the possible reason is that there is a higher electric field between the drain and the source, which makes it easier for the electric field-assisted tunneling effect to occur. In addition, this thesis also proposes a pulsed small signal S-parameter measurement method. After the off-state stress voltage is applied to the device, the S-parameter is measured with a short pulse turn-on voltage. The changes in the small signal parameters are observed when current dispersion occurs. The equivalent circuit model is established and extracts small signal parameters. It can be observed that when the device is turned off with a high drain bias, the intrinsic parameters such as the resistance between the drain and the source (Rds), the capacitance between the gate and the drain (Cgd), and the capacitance between the drain and the source (Cds) all change significantly. The electrons in the channel may be trapped by defects in the AlGaN barrier layer and buffer layer under a high electric field.
顯示於類別:	[電機工程研究所] 博碩士論文

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