How a 2D material with exceptional electron mobility is set to revolutionize electronics and outperform silicon
In the relentless pursuit of technological advancement, as the limits of silicon are tested, scientists are turning to a new class of materials measured in atoms, not millimeters. Among these, one contender stands out with a particularly enticing set of properties: indium selenide (InSe). Dubbed the "golden semiconductor," this material combines the extreme thinness of graphene with the high electron mobility of silicon, creating a potential pathway to faster, smaller, and more energy-efficient electronics for applications from artificial intelligence to autonomous driving 3 5 .
As silicon approaches its physical limits, 2D materials like indium selenide offer a path to continued progress in electronics miniaturization and performance.
With thickness measured in atoms rather than millimeters, 2D semiconductors represent the next frontier in material science and electronics.
Indium selenide belongs to the family of III-VI layered semiconductors 4 . Its structure is like a stack of incredibly thin sandwiches, each composed of four atomic layers in the sequence Se–In–In–Se, all bound together by strong covalent bonds 2 6 . The "magic" happens between these sandwiches, where only weak van der Waals forces hold them together, allowing researchers to easily peel them apart into layers just atoms thick 2 4 .
This unique architecture grants InSe its remarkable electronic properties. It boasts an electron mobility of up to 2,000 cm² V⁻¹ s⁻¹, a measure of how quickly electrons can flow through it. This value is significantly higher than that of silicon and even surpasses other promising 2D materials 2 . Furthermore, with a direct bandgap of around 1.3 eV, InSe can efficiently both absorb and emit light, making it a dual threat suitable for both high-speed electronics and advanced optoelectronics 2 6 8 .
Adding to its versatility, InSe exists in several crystalline forms, or polytypes, such as β, ε, and γ. The γ-phase, with its rhombohedral crystal structure, is particularly prized for its high crystallinity and ease of exfoliation, making it a preferred candidate for research and development 4 .
| Polytope | Crystal System | Band Gap Type | Band Gap Value |
|---|---|---|---|
| β-InSe | Hexagonal | Direct | ~1.28 eV |
| γ-InSe | Rhombohedral | Direct | ~1.29 eV |
| ε-InSe | Hexagonal | Indirect | ~1.4 eV |
Despite its superb qualities, a major hurdle has prevented indium selenide from revolutionizing the electronics industry: wafer-scale production 3 5 . For practical use in chip manufacturing, scientists need to create large, uniform sheets of crystalline InSe. This has proven exceptionally difficult because the indium and selenium elements have vastly different vapor pressures, making it hard to maintain the perfect 1:1 atomic ratio required for a high-quality crystal during traditional high-temperature synthesis 5 .
The challenge lies in maintaining stoichiometric balance - the precise 1:1 ratio of indium to selenium atoms - during high-temperature synthesis due to their different vapor pressures.
For years, the primary method for creating bulk InSe crystals was the Bridgman-Stockbarger technique, which involves heating the constituent elements above 900°C in a sealed capsule and then cooling them very slowly over the course of about a month 4 . While this method can produce high-purity, large crystals suitable for research, it is not ideal for the mass production of uniform wafers .
High-purity indium and selenium are prepared in a precise 1:1 atomic ratio.
Elements are placed in a quartz ampoule which is evacuated and sealed.
The ampoule is heated to over 900°C to melt and combine the elements.
Temperature is slowly decreased over approximately one month to form large crystals.
The resulting InSe crystal is removed from the ampoule for further processing.
In 2025, a team of researchers from Peking University, Renmin University of China, and other institutions unveiled a groundbreaking solution to this manufacturing problem. Published in the journal Science, their work demonstrated a novel "solid-liquid-solid" growth strategy that successfully produced 2-inch wafers of uniform, single-phase crystalline InSe 1 5 .
The team's ingenious process can be broken down into a clear, step-by-step methodology.
This coated wafer is then placed in a container and covered with a lid made of fused silica. The critical step is sealing the edges with liquid indium, creating a closed environment 1 .
The transistor arrays fabricated from these InSe wafers demonstrated performance that signals a true paradigm shift. The devices achieved an average electron mobility of 287 cm² V⁻¹ s⁻¹ and a steep subthreshold swing of 67 mV/decade, very close to the theoretical Boltzmann limit 1 5 . These metrics are not just incremental improvements; they establish a new benchmark for 2D semiconductors and, in key areas, surpass the 2037 projections for silicon laid out by the International Roadmap for Devices and Systems (IRDS) 5 .
| Property | Value | Significance |
|---|---|---|
| Electron Mobility | 287 cm² V⁻¹ s⁻¹ (average) | Surpasses all previously reported 2D film-based devices 5 |
| Subthreshold Swing | 67 mV/decade | Near the theoretical Boltzmann limit, indicating high switching efficiency 1 5 |
| Performance vs. IRDS | Surpassed 2037 projections | Positions InSe ahead of future silicon benchmarks 5 |
| Material / Reagent | Form/Function | Key Use in Research |
|---|---|---|
| Indium (In) | High-purity metal (≥99.999%) | Primary precursor for synthesizing InSe, used in Bridgman method or as a sealing agent 5 |
| Selenium (Se) | High-purity pellets (≥99.999%) | Second precursor; maintaining a 1:1 ratio with Indium is critical for crystal quality 5 |
| Indium Selenide (InSe) | Powder (≥99.995%) or Pre-formed Crystals (≥99.999%) | Starting material for liquid-phase exfoliation to create nanosheets for device testing 2 |
| Sapphire Wafer | Crystalline substrate (e.g., Al₂O₃) | Provides an inert, atomically smooth surface for the deposition and growth of thin InSe films 1 5 |
| Chemical Vapor Transport (CVT) Agent | Iodine (I₂) | Facilitates crystal growth at lower temperatures in sealed ampoules, though can introduce purity concerns 2 |
The potential of indium selenide extends far beyond traditional transistors. Its excellent light-absorption and emission properties make it a prime candidate for high-performance photodetectors with broad spectral response and ultra-fast reaction times 2 . Furthermore, exfoliated InSe nanosheets are being investigated for their role in the hydrogen evolution reaction (HER), a key process for producing clean hydrogen fuel 2 .
With its direct bandgap and high light absorption efficiency, InSe is ideal for photodetectors, solar cells, and LED applications.
InSe nanosheets show promise as catalysts for hydrogen production, potentially enabling more efficient clean energy technologies.
In a fascinating parallel development, other researchers are exploring the material's phase-changing capabilities. One study found that a specific ferroelectric phase of indium selenide (β″-In₂Se₃) can be switched between crystalline and glassy states using a continuous electric current, and without passing through a liquid melt phase 3 . This electrically driven solid-state amorphization could pave the way for ultra-low-power memory storage devices 3 .
The journey of indium selenide from a laboratory curiosity to the brink of commercial application highlights the transformative power of materials science. The recent breakthrough in wafer-scale synthesis is more than just a technical achievement; it is a gateway. By overcoming the long-standing barrier of large-scale production, researchers have unlocked the potential for a new generation of computing—chips that are not only more powerful but also more efficient, fueling progress in artificial intelligence, smart devices, and a connected world we are only beginning to imagine. The "golden semiconductor" has truly arrived, and its future looks brilliantly bright.
With its exceptional properties and now viable manufacturing process, indium selenide is poised to drive the next wave of electronic innovation.