Impact of gate oxide complex band structure on n-channel III–V FinFETs

FinFET geometries have been developed for the sub-22 nm regime to extend Si-CMOS scaling via improved electrostatics compared to planar technology. Moreover, engineers have incorporated high-k oxide gate stacks. Beyond leakage current, less discussed is the impact of the gate oxide's complex band structure on the device performance. However, it defines the boundary condition for the channel wavefunction at the interface, which, in turn, affects the quantum confinement energy for channel electrons. Here we show that the ON-state performance of n-channel FinFETs may be sensitive to the oxide's complex band structure, especially with light-mass III-V channel materials, such as In
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Ga
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As. We study this effect using an ensemble semi-classical Monte Carlo device simulator with advanced quantum corrections for degeneracy and confinement effects. Our simulations suggest that using a surface oxide with a heavy effective mass may lower the channel carrier confinement energies, mitigating unwanted quantum side-effects that hinder device performance. Ultimately, future high-k stacks may benefit from oxide gate stack heterostructures balancing effective mass and dielectric permittivity considerations.