Semiconductors are crucial materials for modern electronic devices. Wide bandgap semiconductor materials have many advantages in these applications, but they are scarce and difficult to synthesize. In this article, we will explore semiconductors, the significance of bandgaps, and discuss a recent study where researchers have discovered a new ultrawide bandgap semiconductor material that could have promising applications in deep ultraviolet optoelectronics devices such as LEDs, lasers, and photodetectors.
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Semiconductors are materials that can conduct electricity under certain conditions and are the building blocks of modern electronic devices such as computers, smartphones, solar cells, and LED lights.
Electricity is conducted in a semiconductor when electrons can move freely from one atom to another. This happens at higher temperatures or when external energy is applied. Semiconductors have a small gap between their valence band (where electrons are bound to atoms) and conduction band (where electrons can move freely). The bandgap determines how much energy is needed to excite an electron from the valence band to the conduction band and vice versa.
The bandgap is one of the key characteristics of semiconductors. A material with a large bandgap requires more energy to conduct electricity or emit light than a material with a small bandgap.
For example, silicon has a bandgap of 1.1 eV (electron volts), which means that it can emit infrared light with wavelengths above 1100 nm (nanometers). On the other hand, gallium arsenide has a bandgap of 1.4 eV, which means that it can emit visible light with wavelengths between 400 nm and 900 nm.
The size of the bandgap also affects how well a material can withstand high voltages and temperatures without breaking down or losing its performance. A material with a large bandgap can tolerate more stress than a material with a small bandgap.
For example, silicon carbide has a bandgap of 3.2 eV, which means that it can operate at temperatures up to 600 °C (degrees Celsius) and voltages up to 10 kV (kilovolts). On the other hand, silicon can only operate at temperatures up to 150 °C and voltages up to 1 kV.
Wide-bandgap semiconductors have many advantages over conventional semiconductors such as silicon or gallium arsenide. They can produce higher power output, higher frequency response, higher efficiency, and lower noise than conventional semiconductors.
Applications and Challenges with Wide-Bandgap Semiconductors
Wide-bandgap semiconductors have promising applications in deep UV optoelectronics devices such as LEDs, lasers, and photodetectors, which can be used for sterilization, water purification, environmental monitoring, and security purposes.
Deep UV light has wavelengths below 300 nm and can effectively kill bacteria and viruses by penetrating deeper into biological tissues and damaging their DNA or RNA molecules. However, producing deep UV light using wide-bandgap semiconductors is challenging as it requires materials with large bandgaps (>4 eV), with only a few materials like aluminum nitride having such large bandgaps.
Wide-bandgap semiconductors can also be obtained by bandgap engineering, which faces challenges during production in controlling growth, doping, avoiding defects and lattice mismatch, optimizing optical and transport properties, and processing into high-quality devices.
Finding new materials with large bandgaps that are stable and easy to fabricate into deep UV optoelectronics devices is therefore an important challenge for researchers in this field.
A Novel Ultrawide Bandgap As2O3 Semiconductor Material
Researchers from Kaduna State University in Nigeria and Ankara University in Turkey have discovered new materials that emit and detect deep UV light. Their study, published in the Journal of Physics: Materials, focuses on low-dimensional materials, particularly two-dimensional oxide semiconductors, as alternatives to silicon-based devices. The researchers propose group VI sesquioxides, specifically As2O3, as a new candidate for semiconductor-related applications due to their unique properties.
The new materials are based on arsenic trioxide (As2O3), a common compound used in medicine and agriculture. They applied pressure or strain to As2O3, creating different crystal structures with wide bandgaps.
The researchers used first-principles calculations based on density functional theory to study the energetic, mechanical, and thermal stabilities of bulk and monolayer structures of As2O3. They found that As2O3 had excellent stability in both forms and came in two different structures: st1-As2O3 and st2-As2O3.
The bandgap of As2O3 decreased uniformly as the number of st1-As2O3 and st2-As2O3 layers increased. Some of the materials had bandgaps wider than 6 eV, which is much higher than those of other known wide-bandgap semiconductors such as gallium nitride (GaN) or silicon carbide (SiC). This high bandgap enables the production of deep UV light with wavelengths below 200 nm, which can penetrate deeper into biological tissues and kill more bacteria and viruses.
Additionally, these As2O3-based materials have high thermal conductivity and low thermal expansion coefficients, making them suitable for high-power and high-frequency electronic devices such as transistors, diodes, and lasers. These properties make them ideal for improving human health and safety.
The discovery of these new As2O3-based materials opens up new possibilities for developing deep UV optoelectronics devices. The researchers hope that their findings will inspire further experimental studies to synthesize and characterize these materials in real conditions. With their potential applications in the medical and agricultural sectors, the development of these materials could have a significant impact on human health and safety.
Semiconductors are essential components of modern electronic devices, and the size of their bandgap plays a critical role in their performance and applications. Wide-bandgap semiconductors, in particular, have significant advantages over conventional semiconductors, and their potential applications in deep ultraviolet optoelectronics are promising.
Producing deep UV light using wide-bandgap semiconductors presents significant challenges, including finding materials with very large bandgaps that are stable and easy to fabricate into devices. The recent discovery of As2O3-based material, a novel ultrawide bandgap semiconductor, presents a promising avenue for future research and development in this field.
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References and Further Reading
Abdullahi, Y.Z., Aybey, R.C., Mogulkoc, Y., Mogulkoc, A. (2023). New stable ultrawide bandgap As2O3 semiconductor materials. Journal of Physics: Materials, 35(8). DOI 10.1088/2515-7639/acc099
Enuh, B.M. (2023). Gallium Nitride Semiconductors in 5G Networks [Online]. AZoM.com. URL https://www.azom.com/article.aspx?ArticleID=22494 (accessed 2.28.23).
Kim, S., Lee, M., Hong, C., Yoon, Y., An, H., Lee, D., Jeong, W., Kim, J.-H., Park, J.-S. (2020). A band-gap database for semiconducting inorganic materials calculated with hybrid functional. Scientific Data, 7(1). DOI: 10.1038/s41597-020-00723-8
Liang, X., Zhang, L., Liu, H., Zhao, J. (2019). Bandgap and band alignment prediction of nitride-based semiconductors using machine learning methods. Journal of Materials Chemistry C, 7(5), pp.1302-1310. DOI: 10.1039/C8TC05554H
Klimov V.I. (2010). Semiconductor Nanocrystals: Structure, Properties, and Bandgap Engineering. Accounts of Chemical Research ,43(2), pp.190–200 DOI: 10.1021/ar9001069
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