Researchers have unveiled a groundbreaking electron localisation phenomenon with the potential to significantly broaden the scope of semiconductor technologies. This discovery promises to enhance the performance of existing semiconductors and extend their applications into fields such as lasers, optical modulators, and photoconductors.
Anderson Localisation, named after physicist P.W. Anderson, describes how elementary quasiparticles like electrons, photons, and phonons behave in disordered semiconductors. This phenomenon occurs when impurities or doping disrupt conduction in metals or semiconductors, leading to a transition from a conducting to an insulating state, known as the Anderson transition.
While traditional Anderson Localisation focuses on geometric defects in lattice structures, physicists Boris I. Shklovskii and Alex L. Efros proposed an alternative model. They suggested that potential fluctuations from random charged dopants could induce a metal-insulator transition, known as the quasiclassical Anderson transition. Experimental confirmation of this model has been elusive until now.
In a significant breakthrough, researchers at Bengaluru’s Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) have successfully demonstrated this quasiclassical Anderson transition.
Using oxygen and magnesium as dopants, the team observed potential fluctuations creating electron ‘bubbles’ in a dielectric matrix, resulting in a percolative metal-insulator transition. This shift in electrical properties occurs without changing the material’s structural integrity.
Led by Associate Professor Bivas Saha, the research team has provided direct experimental evidence of this transition in single-crystalline, heavily doped, and highly compensated semiconductors, with scandium nitride serving as a prime example. Their findings reveal an astonishing nine orders of magnitude change in resistivity, offering new insights into electron localisation behaviour in semiconductors.
The researchers employed a unique approach by utilising a magnesium-compensated scandium nitride semiconductor, deposited under ultrahigh vacuum conditions. This approach not only resulted in the metal-insulator transition but also led to unusual behaviours in carrier mobility, thermopower, and photoconductivity.
The potential fluctuations induced by the random dopant distribution significantly impact resistivity and the electrical transport properties, differentiating them from conventional semiconductor behaviours.
Dr Dheemahi, the Lead Author of the study, highlighted the potential applications of this discovery: “This electronic transition in single-crystalline and epitaxial semiconductors could revolutionise their use in various technologies, including lasers, optical modulators, photoconductors, spintronic devices, and photorefractive dynamic holographic media.”
The ability to manipulate semiconducting properties through potential fluctuations may lead to the development of more efficient semiconductor technologies across multiple disciplines.
Professor Bivas Saha emphasised the significance of their findings: “Our research represents the first experimental confirmation of the quasiclassical Anderson transition and percolative metal-insulator transition in materials. We have demonstrated that potential fluctuations from random dopant distributions can drastically alter electron transport physics, leading to phenomena similar to the Anderson transition in single-crystalline materials. These insights are poised to transform our understanding of electron localisation and its applications in advanced technologies.”
India is enhancing its semiconductor production as part of its digital transformation strategy. Once dependent on importing mobile phones, India now boasts a strong domestic manufacturing ecosystem and is a major exporter. The Prime Minister envisions India as a global leader in semiconductor production, with every piece of equipment featuring a “Made in India” chip. This goal is central to the Indian Semiconductor Mission, which aims to boost technological capabilities and reduce reliance on foreign suppliers.
This focus on semiconductors aligns with India’s broader goals of digital innovation and self-reliance, supporting its ambition to become a developed nation by 2047. The integration of advanced manufacturing in sectors like defence and semiconductor production reflects India’s commitment to building a resilient and competitive economy. As India continues to strengthen its digital and technological infrastructure, it is poised to emerge as a global leader in both defence and digital technology.
