Effects of double passivation for optimize DC properties in gamma-gate AlGaN/GaN high electron mobility transistor by plasma enhanced chemical vapor deposition

Two different materials for double passivation layers have been implemented to an AlGaN/GaN high electron mobility transistor on Si (111) substrate and the improved DC properties are demonstrated. Si ₃N ₄ and SiO ₂ passivation materials are deposited on the gamma gate upper and bottom layers by plasma enhanced chemical vapor deposition. The gamma shape gate can be made by selectively accurate Si ₃N ₄ or SiO ₂ first passivation dry etching with wet etching. The second passivation on gamma gate effectively increases the DC properties. The effects of DC properties of Si ₃N ₄ or SiO ₂ single passivation and Si ₃N ₄/Si ₃N ₄ or SiO ₂/SiO ₂ double passivations are compared. The Si ₃N ₄/Si ₃N ₄ double passivation shows the maximum saturation current density and the peak extrinsic transconductance which increases up to 72% and 18%, respectively, more than Si ₃N ₄ single passivation and also up to 18% and 5% than SiO ₂/SiO ₂ double passivation.