How Semiconductors Are Studied and Created for Nanophotonics

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Between March 27 and May 17, applications are open for the Mirror Lab Project Competition. As part of the new applications campaign, the HSE University bulletin (Okna Rosta) is publishing a series of interviews with the winners of last year's competition. In this issue, Natalia Kryzhanovskaya and Maxim Solodovnik speak about nano- and quantum technologies, as well as cooperation between HSE and Southern Federal University (SFedU).

'The Creation and Study of A3B5 Semiconductor Heterostructures with Quantum Dots for Nanophotonics, Single-photon Emitters, and Micro- and Nanolasers', a joint project between the International Laboratory of Quantum Optoelectronics at HSE University in St Petersburg and the Laboratory of Epitaxial Technologies at Southern Federal University, won the Mirror Lab Project Competition in 2022.

— How, when and under what circumstances were the HSE International Laboratory of Quantum Optoelectronics and the SFedU Laboratory of Epitaxial Technologies created?

— The International Laboratory of Quantum Optoelectronics was established by order of HSE Rector Yaroslav Kuzminov on January 20, 2020, as part of the St Petersburg School of Physics, Mathematics and Computer Science. In 2020, the laboratory team was formed, premises were prepared to accommodate the equipment, and workstations were set up. Research equipment was purchased and used to set up a unique, one-of-a-kind Complex Optoelectronic Stand. In 2022, the laboratory was equipped with additional new scientific measuring instruments. The current set of research equipment enables the study of the properties of semiconductor micro- and nanostructures, as well as devices based on them.

At Southern Federal University, the process was somewhat different. Molecular beam epitaxy and A3B5 semiconductor technology were new areas of research for SFedU, so their laboratory had to be created from scratch, and putting together a team of researchers took quite a while. In 2019, they officially established a separate research group to focus on this area. At first, the group consisted of only four people, and its main research focus was broadly defined as nanoscale structuring of surfaces and the study of epitaxial growth processes of self-organising nanostructures on them.

The two research teams first met at Saint Petersburg OPEN, a conference for young scientists focused on optoelectronics, photonics, and nanostructures. Starting in 2021, this annual conference has been hosted by HSE University-St Petersburg. Since then, the collaboration between our two teams has been expanding, and in 2022, we decided to apply to the Mirror Lab Project Competition held by HSE. Based on the outcome of the competition, the Laboratory of Epitaxial Technologies was set up at SFedU as part of its Institute of Nanotechnology, Electronics, and Instrumentation; today, the laboratory employs ten people.

— Could you tell us more about your project 'The Creation and Study of A3B5 Semiconductor Heterostructures with Quantum Dots for Nanophotonics, Single-photon Emitters, and Micro- and Nanolasers'? What areas of research does it focus on? What are the most interesting results?

— The project aims to study the processes involved in obtaining and creating A3B5 nanostructures with quantum dots that can be positioned as needed to serve as building blocks for integrated optoelectronic and nanophotonic applications, including nano- and micro-sized radiation sources. Quantum dots are semiconductor objects at the nanoscale level that have a spectrum resembling that of atoms, which is why they are sometimes referred to as artificial atoms. By altering the shape and size of such objects, it becomes possible to manipulate their electronic structure, and consequently, their optical properties, including the properties of devices based on them. Arranging such objects in a specific order on a surface presents great opportunities for both exploring new effects and designing novel devices. Creating pits (depressions) of various shapes and densities on the surface enables quantum dot formation in desired locations and broadens the potential for controlling their properties. Despite the apparent simplicity of this approach, researchers encounter numerous scientific and technological challenges in practice that require separate investigation, as many processes in such systems unfold differently and are not yet fully understood. Exploring the structural and optical properties of such objects makes it possible to assess their potential for subsequent application and provides insight into specific aspects of their growth, thereby expanding our ability to manipulate these processes at all levels.

One of the intriguing early findings of our project is that the shape of created pits not only influences the size and shape of the nanostructures growing within them, but also has a direct impact on the process of their formation. In other words, the emergence of these objects can vary depending on the pit in which they are formed. As a result, certain structures become optically and functionally active, while others do not. It is expected that these findings will be presented at the Saint Petersburg OPEN conference.

The project also aims to develop techniques for creating micro- and nanometer-scale optical resonators in heterostructures containing positioned quantum dots, specifically In(Ga)As/GaAs. This represents a step towards the development of devices that are directly based on such structures, specifically micro- and nanoscale sources of optical radiation, including quantum sources. These devices show promise as fundamental building blocks not just for telecommunication systems, but also for integrated sensors, quantum and optical computing, quantum cryptography systems, secure data transmission, and other applications.

— How did you assemble the team of researchers working on the project? How did you initially meet and begin your collaboration? What areas of professional expertise do the teams at your laboratories share?

— Alexey Zhukov, Corresponding Member of the Russian Academy of Sciences, Doctor of Physical and Mathematical Sciences, is the academic supervisor of the International Laboratory of Quantum Optoelectronics. When the laboratory was established in 2020, it had a total of ten staff members, of whom seven were full-time employees. By the time we applied to the Mirror Lab Project Competition, the team had grown to 14 members. The laboratory has since been able to expand its team by involving students in research work. In 2023, a doctoral programme in physics was opened at HSE in St Petersburg, and enrolment in the new Physics of Semiconductors doctoral programme is currently underway. The involvement of Russian postdoctoral fellows through competitive selection at HSE has been a successful experience for the laboratory.

The collaboration between the two laboratories is centred around the unique capability of Southern Federal University’s team to perform epitaxial synthesis of semiconductor nanomaterials in the form of low-density In(Ga)As/GaAs quantum dots and the post-processing of these structures. In turn, the International Laboratory of Quantum Optoelectronics at HSE in St Petersburg provides expertise in optical research of such structures using unique scientific equipment, as well as experience in creating light-emitting devices based on quantum dots.

— What near-future objectives has your project team set for itself?

— One of the areas that the International Laboratory of Quantum Optoelectronics at HSE in St Petersburg has been focusing on is research and development into miniature laser sources and photodetectors for integrated optical and optoelectronic circuits. These circuits are suitable for various applications such as optical transmission and processing of information, as well as optical sensors. We have made significant progress in this direction in recent years, but there are still many scientific and technological challenges that need to be addressed. One of the most important objectives is to improve the performance of our microlasers, surpassing the 10 Gbit/sec achieved so far. We also have great hopes that our proposed solutions will have practical applications.