Progress in Research on Self-Assembled Positioned Growth of Wafer-level Silicon-based Germanium Quantum Wires

[ Instrument R & D of instrument network ] Germanium / silicon quantum wire has the advantages of high hole mobility, low ultra-fine interaction, strong spin-orbit interaction, and silicon compatibility. It has become a silicon-based high-performance spin and even topological quantum computing Material system. Although the non-in-plane growth of quantum wires has made many important achievements in the exploration of novel properties, the lack of in-plane growth of on-demand growth of quantum wires is a bottleneck that hinders the precise addressing and large-scale expansion of quantum devices.

Quantum wires can be used to make transistors. Transistors are the basic components of modern electronic circuits. For manufacturing transistors, the most critical issue is to ensure that the gate can effectively control the opening and closing of the conductive channel. According to Moore's Law, the size of transistors will become smaller and smaller, down to the nanometer level. This makes it more and more difficult to maintain adequate control.

If the gate is fabricated on the periphery of the nanowire and the quantum wire is used as the conductive channel, such a transistor will have excellent conductive characteristics.

Zhang Jianjun, a researcher at the Key Laboratory of Nanophysics and Devices of the Institute of Physics, Chinese Academy of Sciences / National Research Center for Condensed Matter Physics in Beijing, has long been engaged in epitaxial preparation and physical properties research of silicon germanium quantum materials. He realized the in-plane growth of Ge quantum wires on a Si (001) substrate without the use of metal catalysts, which solved the problems of metal contamination and difficulty in large-scale transfer and arrangement of Ge quantum wires grown in the traditional VLS method. In recent years, it has cooperated with domestic and foreign teams to successfully prepare Ge qubits using this quantum wire, and realized the coupling of quantum dots and superconducting microwave resonators.

In electronics, coupling refers to the transfer of energy from one circuit part to another. For example, through conductive coupling, energy is transmitted from a voltage source to the load. The use of capacitors allows the AC component to block the DC component, allowing the AC and DC parts of the circuit to be coupled. The transformer can also act as a coupling medium. By configuring the appropriate impedance at both ends, an appropriate impedance matching can be achieved.

Based on the above research, in order to solve the problem of in-plane Ge quantum wire growth on demand, doctoral students Gao Fei (graduated) and Wang Jianhuan of the research group, under the guidance of Zhang Jianjun, combined nanofabrication and molecular beam epitaxy (MBE) ), Successfully achieved the controlled growth of the position, length, period and structure of Ge quantum wires in the wafer-level plane on the Si (001) pattern substrate. The Ge quantum wire is located on the edge of the groove, and the size is very uniform, without defects, the height is 3.8 nm, the standard deviation is only 0.11 nm, and the length can in principle be arbitrarily long. In addition, an ordered array of closely arranged parallel Ge quantum wires and special structures such as "mouth" and "L" shapes is also realized.

Cooperate with Hu Hao, associate professor of Xi'an Jiaotong University and Liu Feng, professor of University of Utah in the research of growth mechanism, explain the mechanism of preferential nucleation and localized growth of in-plane Ge quantum wires at the edge of the groove; Georgios Katsaros and Professor Daniel Loss of the University of Basel in Switzerland collaborated to observe and understand the spin-orbit coupling strength and InAs, InSb quantum wires are comparable to the electric field control of strong spin orbit effects, and observed tightly arranged quantum wires between quantum dots Capacitive coupling. Graphic structure preparation and material characterization were supported by Wang Guilei, Institute of Microelectronics, Chinese Academy of Sciences and Yao Qi, Institute of Physics. This research work laid an important material foundation for precise addressing and large-scale expansion integration of Ge quantum devices.

Source: Institute of Physics, Encyclopedia