Scientists Unveil First Graphene-Based Chip with Mind-Blowing Electron Mobility — Leaving Silicon in the Dust!
“Innovation is seeing what everybody has seen and thinking what nobody has thought.” — Albert Szent-Györgyi
Scientists based in Atlanta at Georgia Tech have created what they claim to be the first operational semiconductor utilizing graphene. This significant advancement carries the potential to transform the field of electronics, paving the way for faster conventional computers and introducing a novel material for upcoming quantum computers.
In a groundbreaking study, unveiled on January 3rd and led by Professor Walt de Heer from Georgia Tech, the focus centers on harnessing epitaxial graphene — a unique crystal structure where carbon forms a chemical bond with silicon carbide (SiC). This cutting-edge semiconductor material, known as semiconducting epitaxial graphene (SEC) or alternatively, epigraphene, showcases an impressive boost in electron mobility compared to the conventional silicon. This heightened mobility facilitates smoother electron movement through the material, encountering significantly less resistance. The result is the development of transistors capable of seamlessly operating at terahertz frequencies, presenting speeds a staggering ten times faster than the silicon-based transistors currently employed in modern chips.
De Heer explains that the approach employed is a modified version of a straightforward technique that has been recognized for over 50 years. He notes, “When silicon carbide is heated to temperatures exceeding 1,000 °C, silicon evaporates from the surface, leaving behind a surface rich in carbon, which subsequently transforms into graphene.”
Now the question arise is.. What is Graphene?, Why wan’t it used as semiconductor material before?. So let me give you a brief about Graphene before..
Graphene is an incredibly thin and strong material made of carbon atoms arranged in a single layer, forming a hexagonal lattice. Think of it as an ultra-thin sheet, like a single layer of graphite in a pencil. Despite being very thin, graphene is remarkably strong, flexible, and an excellent conductor of electricity.
It has been known since 2008 that Graphene behaves like semiconductor when heated with Silicon Carbide in vaccum but the method outlined in the research paper helps us achieve Graphene semiconductor with better bandgap, a crucial element necessary for transistors to transition between on and off states. Also the earlier methods produces low mobility Graphene semiconductor due to chemical or mechanical makeup.
As stated in the research paper..
“The graphene revolution was originally driven by the search for electronic materials that could outperform silicon. Graphene, which is intrinsically a semimetal (that is, a gapless semiconductor), was considered to be a probable candidate following predictions that, owing to quantum confinement, graphene nanoribbons can be semiconductors. However, efforts to produce high-quality semiconducting ribbons were not successful. Therefore, research focused on altering the electronic structure of graphene chemically, but efforts failed to produce a viable semiconductor. After this, interest shifted away from graphene, towards other two-dimensional (2D) materials that are intrinsically semiconducting”
Production of SEG (SiC-encapsulated graphene) :
The production of SEG (SiC-encapsulated graphene) coated SiC chips involves a meticulous process. A closed cylindrical high-purity graphite crucible is utilized, measuring 14 mm in length and 10 mm in diameter, with a bore size of 5.5 mm. The crucible is sealed with a cap featuring a 1-mm hole. This setup is then placed in a quartz tube and heated inductively, with temperatures monitored using an optical pyrometer. The sandwich structure consists of two 3.5 × 4.5 mm SiC chips, with the top chip’s Si face facing the C face of the bottom chip. The process involves annealing in three phases, including surface cleaning in high vacuum at 900 °C, high-temperature pre-growth annealing at 1,300 °C, and a final annealing step at about 1,600 °C. During this process, the Si face of the top chip develops atomically flat terraces covered with a buffer layer. The use of a graphitized polymer aids in establishing the necessary temperature differential between the top and bottom chips. The study explores alternative crucible designs and temperature gradient control for optimizing growth parameters. The researchers also investigate SEG (SiC-encapsulated graphene) stability under various conditions, demonstrating its stability in saturated silicon vapor. The study concludes that SEG-coated (0001) faces exhibit greater stability than bare (0001) faces and other SiC crystal faces, providing insights into the preference for SEG-coated (0001) facets in SiC deposition. Further research aims to optimize parameters and explore alternative crucible designs for improved temperature control during the production of SEG-coated SiC chips.
As stated earlier, the idea of Graphene based semiconductor existed before but its the method deployed by Heer helps us achieves better bandgap in the graphene semiconductor. The semiconductor produced demonstrates better mobility with regular bonding as stated by Heer below
“If it is done correctly, using the modified method described above, then the bonding is very regular and the mobility is very large, as we have shown in the paper,”
“One main aspect of graphene electronics is that we can utilize the quantum-mechanical wave properties of the electrons and [electron] holes which are not accessible in silicon electronics,” says de Heer. “If this is possible, then that constitutes a paradigm shift in electronics.”
Semiconductors, crucial for all our electronic gadgets, act like both conductors and insulators. Yet, silicon, the main material for these semiconductors, is facing challenges in terms of speed, heat, and making things smaller. De Heer points out that the rapid advancements we’ve seen in the history of computers are slowing down because silicon is reaching its limits.
Now, let’s delve a bit more into why silicon is having a tough time. As we try to make devices faster, they generate more heat. Silicon has a hard time handling this increased heat without losing efficiency. Additionally, as we aim to make everything smaller and more compact, silicon faces difficulties maintaining its performance. So, while silicon has been incredible for the growth of technology, it’s like a road that’s getting a bit crowded and slowing down the traffic of progress. Researchers are now on the lookout for new materials to keep the journey of innovation smooth and fast.
In the end, here’s what the lead scientist De Heer have to say on this breakthrough.
“It will take time to develop this technology. I compare this work to the Wright brothers’ first 100-meter flight. It will mainly depend on how much work is done to develop it.”
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