III–V Metal–Oxide–Semiconductor Field-Effect Transistors with High κ Dielectrics

Research efforts on achieving low interfacial density of states ( D it ) as well as low electrical leakage currents on GaAs-based III–V compound semiconductors are reviewed. Emphasis is placed on ultra high vacuum (UHV) deposited Ga 2 O 3 (Gd 2 O 3 ) and atomic layer deposition (ALD)-Al 2 O 3 on GaAs and InGaAs. Ga 2 O 3 (Gd 2 O 3 ), the novel oxide, which was electron-beam evaporated from a gallium-gadolinium-garnet target, has, for the first time, unpinned the Fermi level of the oxide/GaAs heterostructures. Interfacial chemical properties and band parameters of valence band offsets and conduction band offsets in the oxides/III–V heterostructures are studied and determined using X-ray photoelectron spectroscopy and electrical leakage transport measurements. The mechanism of III–V surface passivation is discussed. The mechanism of Fermi-level unpinning in ALD-Al 2 O 3 ex-situ deposited on InGaAs were studied and unveiled. Systematic heat treatments under various gases and temperatures were studied to achieve low leakage currents of 10 -8 –10 -9 A/cm 2 and low D it 's in the range of (4–9) × 10 10 cm -2 eV -1 for Ga 2 O 3 (Gd 2 O 3 ) on InGaAs. By removing moisture from the oxide, thermodynamic stability of the Ga 2 O 3 (Gd 2 O 3 )/GaAs heterostructures was achieved with high temperature annealing, which is needed for fabricating inversion-channel metal–oxide–semiconductor filed-effect transistors (MOSFET's). The oxide remains amorphous and the interface remains intact with atomic smoothness and sharpness. Device performances of inversion-channel and depletion-mode III–V MOSFET's are reviewed, again with emphasis on the devices using Ga 2 O 3 (Gd 2 O 3 ) as the gate dielectric.