Sub-Picosecond Nanodiodes for Low-Power Ultrafast Electronics

Continuous research to advance modern electronics is important to boost their overall performance and expand their applications. Today, the demand for low-power electronic devices with ultrafast response and ultra-high-speed has significantly increased. However, the trade-off between low power and ultrahigh-speed remains the biggest challenge in improving the performance of modern electronics. Additionally, despite the impressive progress in addressing the trade-off issues, other challenges and barriers inhibiting the development of low-power ultrafast electronics, including manufacturing capability limit, heat death effects, carrier velocity restriction and short-channel effects, are yet to be fully addressed. These challenges hinder operation speed enhancement at low operating voltages, limiting the practical applications of such electronic devices. Therefore, developing effective design strategies for overcoming these inherent challenges is highly desirable.

Two-dimensional (2D) semiconducting electronic nanodevices have emerged as promising candidates for addressing the high-speed problems owing to their short-channel immunity and remarkable carrier transport. Nevertheless, their response time is still limited by the serous lattice collision scattering. Consequently, the possibility of achieving ultrafast electrical responsible by improving carrier velocity has been investigated. Emerging nanoplasma-enabled device has reported the electrical response in 5 picoseconds. But its practical application is hindered by numerous problems associated with high operating voltages, weak rectifying chrematistics, current leakages, structural limitations and fabrication difficulties. Notably, there are no studies on ultrafast sub-picosecond electric nanodevices with improved rectifying characteristics at low operating voltage matching that of modern electronic integrated chips. This is an interesting research area considering its potential contribution for ultrafast electronic devices operating at low voltages (less than 2V) for future integrated chips.

To address these challenges, Dr. Nannan Li, Binglei Zhang, Dr. Yue He and led by Professor Yi Luo from the Microsystem & Terahertz Research Center of CAEP fabricated a novel coplanar tip-to-edge metal-based nanostructure with asymmetric sub-10 nm air channel and demonstrated its sub-picosecond electrical response at a low turn-on voltage approximately 0.7V. The rectifying characteristics and electrical response of the resulting nanostructure was examined and compared to those of promising 2D semiconducting nanodiodes. The feasibility of the fabrication approach in addressing the dominant challenge of the trade-off issues was also investigated. Their research work is currently published in the research journal, Advanced Materials.

The researchers reported that the coplanar asymmetric nanostructure achieved an extremely shorter electrical response time of 64 fs at a turn-on voltage of 0.7V. This was attributed to the ultralow voltage tunneling emission and scattering free-electron transportation without heat limit in the accelerated and intensive electric field in the short air channel. The resulting ultrafast nanodiode exhibited an excellent rectifying ratio of up to 10^6, which is significantly higher than that of existing promising semiconducting nanodiodes. Additionally, the inherent problem of heat death was effectively addressed by less heat generation, low power consumption and improved heatsinking capability due to the novelty and the underlying working mechanism of the nanostructure.

In summary, the study successfully reported the fabrication of a novel coplanar asymmetrical tip-to-edge semiconductor-free nanostructure capable of achieving ultrafast sub-picosecond electrical response with lower power consumption. An impressive record ultrafast response time broke the physical limitations of the semiconductor. The fabricated nanostructure demonstrated superior performance compared to the fasted low-power electrical devices to ever been reported. The potential application of the intriguing nanodiodes as rudimentary building blocks in ultrafast and low-power electronic integrated circuits will attract broad interests in designing high-performance electronics. In a statement to Advances in Engineering, Professor Yi Luo said that the present novel nanodevice offers a feasible route for overcoming the dominant trade-off between high speed and low power in modern electronics, promising significant breakthroughs in the design of next-generation ultrafast electron integrated chips and systems.