利用氮化鋁/氮化矽作為閘極介電質及鈍化層之低電流崩潰氮化鎵金屬絕緣層半導體高速電子遷移率電晶體

Abstract

氮化鎵基板高電子遷移率晶體管在國防和通信系統表現出出色的高功率和高頻率的應用。然而，會發生許多不好的效應，例如電流崩潰和增加動態導通電阻由於表面陷阱和材料的高極化特性。由於氧化系材料會產生一些氧化作用，像是在表面生成氧化物、界面產生氧化擴散，所以在氮化鎵的鈍化層上利用氮化系材料會是很好的選擇。氮化矽已被證實為有效的鈍化介電質，可以減少表面狀態，並有效抑制在氮化鎵電晶體的電流崩潰，然而，卻沒有足夠高的能帶(~5eV)來抑制漏電流。氮化鋁具有較大的能帶(~6.2eV)能有效地降低漏電流。在我的研究裡，證實了利用氮化鋁/氮化矽在氮化鎵金屬絕緣層半導體的鈍化層上結合了氮化鋁和氮化矽的優點。為了比較氮化鋁/氮化矽在氮化鎵金屬絕緣層半導體的鈍化層的特性，也準備了單層鈍化層結構。晶片被分成三個樣本。總之，氮化矽已被證實，它在氮化鎵鈍化層具有很多很好的效果，如降低通道電阻、低表面狀態、低界面陷阱密度和低電流崩潰效應。氮化鋁具有高能帶能抑制漏電流，但是它會增加導通電組，並導致嚴重的電流崩潰效應。在我的研究中，氮化鋁/氮化矽雙層介電質和段化層已經被證實可以減少氮化鎵金屬絕緣層半導體的電流崩潰效應和漏電流。

Gallium nitride-based high-electron-mobility transistors (HEMTs) have demonstrated outstanding performance for high-power and high-frequency applications for defense and communication systems. However, there are many undesirable effects such as current collapse and increase in dynamic ON-resistance due to the surface donor states and the high polarization nature of the material. Nitride-based materials are more desirable for GaN passivation because the oxide-based materials have many oxygen contaminations on GaN. SiN has been proved as an effective passivation dielectric to reduce the surface states and can efficiently suppress current collapse in the GaN HEMTs. However, the bandgap of SiN (∼5 eV) is not high enough to suppress leakage current. AlN has a large bandgap (∼6.2 eV) can effectively reduce leakage current as passivation layer. In this work, we demonstrate GaN MIS-HEMT using AlN/SiN bilayer gate dielectric and passivation layer which combine the advantages of SiN and AlN. For comparing the performance of GaN MIS-HEMT with AlN/SiN bilayer gate dielectric, we also prepared reference devices with single layers dielectric. The wafer was divided into three samples after mesa and ohmic contact process. In conclusion, SiN was been proved that it has many good effects for GaN passivation such as decreasing of channel resistance, low surface state, low interface trapping density and low current collapse effect. AlN with high bandgap nature can suppress the leakage current. However, it would increase channel resistance, and cause severe current collapse effect. In this study, an effective AlN/SiN bilayer dielectric and passivation layer have been demonstrated for reducing current collapse effect and leakage current in GaN MIS-HEMT.