In the semiconductor industry, there is a lot of research and development (R&D) being done on carbon materials. This is because carbon has many potential applications in semiconductors. However, there is still some debate about whether or not carbon actually qualifies as a semiconductor.
In this blog post, we will explore if Carbon is a semiconductor, the properties of a semiconductor and whether or not Carbon has them, and other semiconductor materials that belong to the same group as carbon. Keep on reading as we dissect everything related to carbon and its semiconductive capabilities.
What Is A Semiconductor?
You may have heard the term semiconductors a lot. But what exactly is a semiconductor? Semiconductors are materials that have an electrical conductivity that is higher than an insulator or non-conductor but lower than a conductor. Let us explain this statement. Only the electrons on the outer shells which are called valence electrons can carry a charge. These have to be free electrons that can move around for them to conduct electricity. When the outer shell is too close to the nucleus or the shell is filled to the maximum number, the bonds holding the electrons stopping them from moving are much stronger.
This means there is a higher chance for elements to be conductors (mostly metals), insulators, or non-conductors than semiconductors since so many criteria must be met to be one. Ideally, electrical conductivity increases to a certain point in a semiconductor material in a non-linear manner and its valence electrons should be able to jump into a conduction band becoming conduction electrons able to carry a charge.
Semiconductors can either be pure elements like silicon or compound materials like Gallium Arsenide or Silicon Carbide, etc. So where does carbon fall? Read to find out.
What Is Carbon And Is It A Semiconductor?
Carbon is a unique non-metal that has the ability to make bonds with other Carbon atoms. At first glance, pure Carbon atoms do not look like they are not semiconductor materials. This is because its valence electrons are too close to the nucleus, and the covalent bond formed is too strong for electrons to move freely.
As mentioned above, the electrons need to be able to move around to conduct electricity which pure Carbon doesn’t have. Semiconductors also need to have an energy gap/band gap of at least 0.6eV to 3.4eV to be a semiconductor but Carbon has a high band gap of 5.5eV to 7eV. Although there is no hard and fast rule that any element with band gaps with electrical energy higher than 3.4eV is an insulator, that is the most common scenario.
However, its semiconductor property can be induced albeit it is forced and with Carbon being combined with other elements or using the other forms of crystalline Carbon which we will explore below. To simply answer the question, Carbon has semiconductor properties that do need some help to show out. Some Carbon allotropes can show these properties even if the pure atom cannot.
The Properties Of Carbon
As mentioned above, Carbon can form covalent bonds with itself. This helps Carbon in its various forms, and the most common is the crystal structure it develops as in Diamond and Graphite. With exposure to the right amounts of heat energy and other conditions, doping methods, and other techniques, some of these allotropes can show semiconductive properties.
Allotropes Of Carbon
Below are three allotropes of Carbon along with their key features and their possible semiconductive capabilities.
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Amorphous Carbon
This form of carbon does not have a crystalline structure and is most commonly found in a powder-like state. Coke and charcoal are two examples of amorphous carbon and can easily be understood not to have any electrical conductivity. However, although amorphous carbon on its own cannot show semiconductive properties, doping with Nitrogen has proven to induce these properties. The key takeaway is that amorphous carbon in its pure form cannot be a semiconductor.
Diamond
This allotrope of Carbon, in its purest form, is an electrical insulator that cannot conduct electricity because of the tight bonds between atoms to atoms, and valence electrons to other valence electrons. The exception to natural diamonds that display semiconductive properties would be the natural blue diamond, in which some Carbon atoms have been replaced by Boron.
These natural diamonds with boron along with synthesized diamond that has undergone doping using boron atoms come under the category of a p-type semiconductor. Chemical vapor deposition (CVD) is another process that dopes diamonds with phosphorus, creating an n-type semiconductor. Heavy doping of Boron atoms has been shown to make diamonds a superconductive element.
It also has a huge potential as a wide bandgap semiconductor due to its ability to power electronic devices at a much faster switching rate than other semiconductors. However, its physical properties are a longstanding challenge that is difficult to evade without extensive treatment and investment. You can learn more information about diamonds as wide bandgap semiconductors in the linked article.
Graphite
This allotrope of Carbon has one free electron while its other three electrons have formed covalent bonds with other Carbon atoms. Due to its large amount of decentralized electrons, Graphite is mostly known as a conductor. However, the more an electron is exposed to faster time scales, specifically when it is subjected to extremely fast time scales (in the scale of femtoseconds (10-15s)), Graphite is known to show semiconductive properties, citing a possibility for usage in electronic devices powered by Carbon.
Carbon Vs Other Semiconductive Group IV Elements
Carbon is not usable as a semiconductor in its purest form and therefore does not fall under the category of intrinsic semiconductors which are conductors made of completely pure elements like Silicon (Si) and Germanium (Ge). Carbon’s electrons are also pretty tightly bonded so becoming charge carriers is quite a challenge for the electrons in its valence band.
On the contrary, this is not the same as Silicon and Germanium, two other semiconductor materials belonging to the same group as Carbon on the periodic table. Silicon is the most commonly used of the two considering its ease of availability while Germanium is harder to source yet widely used, especially in comparison to Carbon. However, both Silicon and Germanium cannot match the effectiveness of vacuum tubes and their high-power capabilities.
Here’s where Carbon’s allotrope, diamonds make their grand entry. Diamond’s ability to power high-power electronics within a solid state. This would result in more compact-sized, efficient, and comparatively low requirements of operational voltage than vacuum tubes. The downside is that diamonds are challenging to work with which is why the preferred semiconductor is most often Silicon or Germanium.
Semiconductors: The Present And The Future Of Technology
Carbon’s semiconductor properties should be forced out in comparison to other materials like Silicon and Germanium which demonstrate their semiconductive properties more easily. These elements are more commonly used in semiconductor devices and integrated circuits, while Carbon needs to undergo more intensive treatments to show a higher conductivity than its popular counterparts that are lower in the periodic table.
Semiconductors, since their inception, have become a major component in technological advancement and they will continue to do so. They are used in everything from mobile phones and household appliances to vehicles and more. Semiconductor technology is evolving as we speak and there will be more advanced devices in the near future. Inquivix Technologies is a premium semiconductor component supplier based in South Korea. To learn more about our products and services please visit our website or contact us.
FAQs
In its purest form, a Diamond is not a semiconductor. However, a natural blue diamond with Boron atoms replacing some Carbon atoms is a semiconductor.
Silicon is the most abundant element after Oxygen and due to its nature as an intrinsic semiconductor, its semiconductive properties can be easily utilized. This ease of availability and application has made silicon chips common in semiconductor fabrication.