ALD Al2O3 passivation of Lg = 100 nm metamorphic InAlAs/InGaAs HEMTs with Si-doped Schottky layers on GaAs substrates

Abstract In 0.52 Al 0.48 As/In 0.7 Ga 0.3 As metamorphic high-electron-mobility transistors (mHEMTs) on GaAs substrates have been demonstrated. The devices feature an epitaxial structure with Si-doped InP/In 0.52 Al 0.48 As Schottky layers, together with an atomic layer deposition (ALD) Al 2 O 3 passivation process. In comparison to the GaAs mHEMTs with plasma enhanced chemical vapor deposition (PECVD) SiN passivation, the devices with ALD Al 2 O 3 passivation exhibit more than one order of magnitude lower gate leakage current ( J g ) and much lower contact resistance ( R C ) and specific contact resistivity ( ρ C ). 100-nm gate length ( L g ) In 0.52 Al 0.48 As/In 0.7 Ga 0.3 As mHEMTs with Si-doped InP/In 0.52 Al 0.48 As Schottky layers and ALD Al 2 O 3 passivation exhibit excellent DC and RF characteristics, such as a maximum oscillation frequency ( f max ) of 388.2 GHz.