氮化鋁鎵/氮化鎵高速電子遷移率場效電晶體在用於高速和高功率開關應用引起了相當大的興趣，因為氮化鎵材料有傑出的電子特性包括二維電子(2DEG)電荷密度(>〖10〗^13 〖cm〗^(-2))、高導熱係數(>2 W〖cm〗^(-1) K^(-1))和高崩潰電場(3.3 MV/cm)。這些特性使氮化鋁鎵/氮化鎵元件崩潰電壓可以到達百伏特或千伏特。然而，對高功率元件的可靠性與穩定性來說表面漏電流是一個嚴重的問題。
本論文提出兩個方法來解決由表面缺陷造成表面漏電流問題:(1) 先鈍化層製程 (2) 氮氣電漿處理在陰極跟飄移區域。這兩種方法用來保護表面，避免在做歐姆接觸時，所使用高溫退火而在表面形成氮氣空位缺陷。
首先，先鈍化層製程方法可以減少表面漏電流二個級數(從〖10〗^(-9) mA 到 〖10〗^(-11) mA)。片電阻可以降低70%。氮氣電漿處理在陰極造成導通電壓下降，對掘入12奈米深的陰極從0.68V到0.4V，對掘入30奈米深的陰極從0.52V到0.16V，我們也討論氮氣電漿處理瓦數對元件的影響，高瓦數的氮氣電漿處理在陽極，導通電壓降低，逆偏漏電流稍微減少。另外一方面，氮氣電漿處理在飄移區域可以減少逆向漏電流。

AlGaN/GaN HEMT have attracted considerable interests for high speed and high power switching application due to the outstanding electronic properties including high sheet charge density (>1013 cm-2) of the two dimensional electron gas (2DEG), high thermal conductivity of GaN (>2 Wcm-1k-1) and high breakdown field (3.3 MV/cm), which allows to fabricate devices with breakdown voltages in the order of hundreds and even up to thousands of volts. However, one of the most critical issues to be solved is the surface leakage current, which is mainly related to reliability and stability for power electronics applications.
This thesis focuses on AlGaN/GaN heterojunction Schottky barrier diodes (SBDs) on Si substrate for power electronics applications. For high power applications, the surface control process was investigated to suppress leakage current in GaN-on-Si devices by using two different approaches, including a passivation first process and a nitrogen plasma treatment process. Both two approaches are proposed to protect surface from producing N-vacancy defects during high temperature annealing for ohmic contact formation and further suppress the leakage current by recovering nitrogen-vacancy-related defects.
First, a passivation first approach is proposed to reduce the surface leakage current from ~10-9 A to ~10-11 A and reduce the sheet resistance up to 70% compared with the SBDs without passivation first. Second, the devices with the nitrogen plasma treatment show a reduced VON from 1 V to 0.7 V for 12-nm recess SBDs and a reduced VON from 0.8 V to 0.4 V for 30-nm recess SBDs, comparing with that of the devices without nitrogen plasma treatment. We also investigated the impact of the plasma power on the device characteristics. With a higher power of plasma treatment on anode region, the turn-on voltage can be reduced with slightly degradation of reverse leakage current. On the other hand, the plasma treatment on the drift region could reduce the reverse leakage current.

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