Researchers at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Md., have demonstrated a novel and groundbreaking way to additively print gallium nitride based on a combination of liquid and gas. Their work was detailed in “A pathway to compound semiconductor additive manufacturing,” published recently in the journal MRS Communications.
“Gallium nitride is a material of significant interest for optoelectronic applications, solar power generation, and high power distribution,” says Jarod Gagnon, a materials scientist in APL’s Research and Exploratory Development Department and lead author on the paper. “Being able to 3D-print semiconductors gives us the ability to make complex devices that are either too costly or too complex to make with current techniques. If we are successful with our research, this will open a new path forward for a rapid change in how we operate in the semiconductor and electronic device field.”
GaN printing represents a new category of 3D printing that Dr. Gagnon and his colleagues call “gas-phase reactive AM.” The team combined additive manufacturing techniques — in this case, material extrusion — with semiconductor synthesis techniques (liquid phase epitaxy and metalorganic chemical vapor deposition) to react with the material as it is printed. “This is what allows us to form single-crystal oriented material through epitaxial growth,” he explains.
“I approached this problem from a semiconductor viewpoint and realized that we could modify and combine existing processes in both research areas to create something new and effective,” he said. “That isn’t to say it wasn’t still a difficult challenge. Additive manufacturing processes and semiconductor processes both have a wide number of critical variables that affect the quality of the final product. Now that we’ve proven the viability of our process, we have double the number of variables that interrelate and have to be controlled and understood to demonstrate the ultimate quality and resolution of our process.”
The requirements for the process, in terms of controlling impurities and safety, were so novel that the team — which includes Michael Presley, Nam Le, Timothy Montalbano and Steven Storck — had to design and build a system that would allow them to perform the research, creating a new capability at APL in the process. The team is now looking for ways to improve resolution and better understand the mechanisms through modeling and experimentation.
