Scientists at Linkoping University have developed a molecule that will facilitate the production of indium nitride. The new material will make it possible to extend the bandwidth available for wireless data transfer by opening access to ever higher transmission frequencies.
Professor Pederson, professor of inorganic chemistry at the Department of Physics, Chemistry, and Biology (IFM) at Linkoping University, led the research, which was published in the journal Chemistry of Materials.
The Key Property of Indium Nitride
Indium Nitride is a semiconductor, and it is a candidate material for use in the fabrication of transistors. The fundamental property that drives the attractiveness of indium nitride, a substance consisting of nitrogen and the metal indium, is the ease at which electrons can move through the material.
Henrik Pedersen described, “Since electrons move through indium nitride quite easily, it is possible to send electrons backward and forwards through the material at very high speeds, and create signals with extremely high frequencies. This means that indium nitride can be used in high-frequency electronics, where it can provide, for example, new frequencies for wireless data transfer.”
A thin layer of indium nitride on silicon carbide. Image credited to Linkoping University
The Difficulties Involved in Producing Thin Films of Indium Nitride
Chemical vapor deposition (CVD), the method most often used to produce thin films of semiconductor materials, involves heating to temperatures in the range of 800 to 1,000ºC. The problem is that indium nitride breaks back down into indium and nitrogen at 600ºC.
Atomic Layer Deposition
Atomic Layer Deposition (ALD) is a method that can be successfully employed to produce a thin layer of indium nitride. The process starts by introducing a gas containing indium into a vacuum chamber to react with the thin film’s substrate. Next, a gas containing nitrogen is introduced to reacts with the surface, forming a monolayer of indium nitride.
The process is repeated often, in a process known as epitaxial growth, until the proper depth of the thin film is built. This process can take place at 300℃, well below the breakdown range of 800 to 1,000ºC.
The researchers developed indium triazenide, a new molecule for the ALD process. They also employed silicon carbide as the target substrate. As per Pedersen, “The molecule that we have produced, an indium triazenide, makes it possible to use indium nitride in electronic devices. We have shown that it is possible to produce indium nitride in a manner that ensures that it is sufficiently pure to be described as a true electronic material.”
An Unexpected Result
During the ALD process, molecules are not allowed to be broken down or react during the gas phase. In the course of their investigations, when the researchers changed the coating process’s temperature, they discovered that there were two temperatures at which the process was stable.
Pedersen noted that “The indium triazenide breaks down into smaller fragments in the gas phase, which improves the ALD process. This is a paradigm shift within ALD – using molecules that are not fully stable in the gas phase. We show that we can obtain a better final result if we allow the new molecule to break down to a certain extent in the gas phase.”
The group is now exploring similar types of triazenide molecules with metals other than indium. The results obtained when using them to produce molecules for ALD have been promising.