Researchers from the University of California, Santa Cruz, and the University of Konstanz in Germany have recently published a study in the journal Physical Review Applied that sheds light on the challenges and potential solutions for reliable charge transport in silicon-based metal-oxide-semiconductor (SiMOS) devices. The team, led by Jack J. Turner and Guido Burkard, has been exploring the impact of device imperfections on electron shuttling in these systems.
The researchers focused on a specific type of charge transport known as conveyor-belt shuttling, which has been well-established in silicon/germanium (Si/SiGe) systems but is still in its early stages for SiMOS devices. To better understand the factors affecting this process, the team performed full 3D simulations of a realistic SiMOS device, building on earlier 2D modeling efforts. They examined the effects of varying shuttling speeds and gate voltages, as well as potential pitfalls such as oxide-interface roughness, gate fabrication imperfections, and charge defects along the transport path.
The simulations revealed that at low clavier-gate voltages, the additional oxide screening in multi-layer gate architectures can cause conveyor-belt shuttling to collapse into a bucket-brigade mode, resulting in considerable orbital excitation. To restore conveyor-belt operation, the researchers found that increasing the confinement was effective. They also discovered that this mode of operation is robust against interface roughness, gate misalignment, and charge defects buried in the oxide. However, defects located at the Si/SiO2 interface can induce significant orbital excitation, and for lower conveyor gate biases, positive defects in the transport channel can even capture passing electrons.
The study highlights key challenges and identifies operating regimes for reliable charge transport in SiMOS architectures. This research is particularly relevant to the energy sector, as SiMOS devices have potential applications in energy-efficient electronics and quantum computing, which could lead to more sustainable and powerful energy solutions. By understanding and addressing the imperfections in these devices, the energy industry can work towards developing more robust and efficient technologies.
Source: Turner, J. J., Binder, C. W., Burkard, G., & Fisher, A. J. (2023). Modelling the Impact of Device Imperfections on Electron Shuttling in SiMOS devices. Physical Review Applied.
This article is based on research available at arXiv.