The team creates the world’s smallest and fastest nano-excitonic transistor.

How is it possible for the diminutive Ant-Man character in the Marvel films to generate such powerful energy? The transistors on his suit, which amplify weak signals for processing, hold the key. Semiconductors that enhance electrical signals in the ordinary manner lose heat energy and break the speed of sign exchange, which debases execution. What if these limitations could be circumvented and a lightweight, compact, and energy-saving high-performance suit constructed?

A nano-excitonic transistor utilizing intralayer and interlayer excitons in heterostructure-based semiconductors, jointly developed by a team from ITMO University in Russia led by Professor Vasily Kravtsov and Professors Kyoung-Duck Park and Yeonjeong Koo from the Department of Physics, addresses the limitations of existing transistors. The study was recently presented in the ACS Nano journal.

Due to the free conversion between light and material in their electrically neutral states, excitons are essential for developing a next-generation light-emitting element with less heat generation and a light source for quantum information technology. Excitons are also responsible for the light emission of semiconductor materials.

“The nano-excitonic transistor is expected to play a key role in the realization of an optical computer, which will aid in the processing of massive amounts of data generated by AI technology.”

Yeonjeong Koo, one of the co-first authors of the research paper,

A stack of two distinct semiconductor monolayers, known as a semiconductor heterobilayer, contains two distinct types of excitons: the excitons within the layers, which have a horizontal and vertical orientation, respectively.

The two excitons produce distinct optical signals with distinct durations, coherence times, and lights. A two-bit exciton transistor could thus be developed with selective control of the two optical signals. Due to the non-homogeneity of semiconductor heterostructures, the low luminous efficiency of interlayer excitons, and the light’s diffraction limit, controlling intra- and interlayer excitons in nanoscale spaces proved to be challenging.

In a previous study, the team proposed a method for pressing semiconductor materials with a nanoscale tip to control excitons in nanoscale spaces. This time, the researchers were able to control the excitons’ density and luminance efficiency from a distance using polarized light at the tip for the first time without physically touching the excitons. The ability to reversibly control excitons, which minimizes physical damage to the semiconductor material, is this method’s most significant advantage, which combines a photonic nanocavity and a spatial light modulator. Additionally, a light-based nano-excitonic transistor can aid in the processing of enormous amounts of data at the speed of light while minimizing the loss of heat energy.

Artificial intelligence (AI) has entered our lives more rapidly than we ever anticipated, and in order to provide useful answers to users, it requires enormous amounts of data. As AI is used in more and more fields, more and more data needs to be gathered and processed. A fresh approach to data processing that is appropriate for this data explosion era is anticipated from this study. “The nano-excitonic transistor is expected to play an integral role in realizing an optical computer, which will help process the huge amounts of data driven by AI technology,” stated Yeonjeong Koo, one of the co-first authors of the research paper.

More information: Yeonjeong Koo et al, Nanocavity-Integrated van der Waals Heterobilayers for Nano-excitonic Transistor, ACS Nano (2023). DOI: 10.1021/acsnano.2c11509