Abstract
This paper reviews our previous theoretical studies and gives further insight into phonon scattering in 3D small nanotransistors using non-equilibrium Green function methodology. The focus is on very small gate-all-around nanowires with Si, GaAs or InGaAs cores. We have calculated phonon-limited mobility and transfer characteristics for a variety of cross-sections at low and high drain bias. The nanowire cross-sectional area is shown to have a significant impact on the phonon-limited mobility and on the current reduction. In a study of narrow Si nanowires we have examined the spatially resolved power dissipation and the validity of Joule's law. Our results show that only a fraction of the power is dissipated inside the drain region even for a relatively large simulated length extension (approximately 30 nm). When considering large source regions in the simulation domain, at low gate bias, a slight cooling of the source is observed. We have also studied the impact of the real part of phonon scattering self-energy on a narrow nanowire transistor. This real part is usually neglected in nanotransistor simulation, whereas we compute its impact on current---voltage characteristic and mobility. At low gate bias, the imaginary part strongly underestimated the current and the mobility by 50 %. At high gate bias, the two mobilities are similar and the effect on the current is negligible.
Highlights
Three-dimensional field effect transistor structures, such as nanowires and FinFETs, have been extensively investigated
This is reflected through the form factors [5,7] that appear in the calculation of the electron–phonon scattering self-energies in the mode description
In this work we investigate ultra-scaled nanowire GAA transistors made of GaAs and InGaAs core
Summary
Three-dimensional field effect transistor structures, such as nanowires and FinFETs, have been extensively investigated. The physical reason is the strong localization of the electron wave function of the channel cross-section This is reflected through the form factors [5,7] that appear in the calculation of the electron–phonon scattering self-energies in the mode description. As the charge of the channel increases, the height of the barrier decreases slowly in the full self-energy case This effect tends to decrease the difference between the two currents while increasing gate bias. This is due to the increasing impact of the channel charge in the channel electrostatic, which modifies the source–drain barrier
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