Researchers identify carbon contamination as key barrier in gallium oxide electronics

Cornell researchers have uncovered a virtually invisible offender hindering the event of next-generation, high-power electronics: a microscopic layer of carbon contamination, typically left behind by air publicity and fabrication methods, that impairs electrical circulation in units made with gallium oxide. They’ve additionally discovered an answer.

A study printed June 20 within the journal APL Supplies is among the many first to straight visualize this nanometer-thin barrier that may happen when metals are patterned onto semiconductors, a vital interface for getting present out and in of digital units. When these contacts have resistance, machine efficiency suffers.

The problem is very pronounced in beta gallium oxide, a semiconductor materials with an ultra-wide band hole that might someday permit units like electrical automobiles and grid infrastructure to extra effectively deal with greater voltages.

“It has been an issue within the gallium oxide discipline for fairly a while,” stated Naomi Pieczulewski, a doctoral pupil in supplies science and engineering and the research’s co-lead writer. “Generally you get good conduction and typically you get completely no conduction in any respect, and nobody might actually pinpoint why.”

Pieczulewski’s analysis spans a number of Cornell labs uniquely positioned to analyze the issue, together with one specializing within the manufacturing of oxide supplies and one specializing in atomic-resolution microscopy.

Specializing in the interface between a beta gallium oxide and titanium contact, Pieczulewski and colleagues used scanning transmission electron microscopy and different methods to check two frequent strategies for fabricating the contact: a conventional lift-off course of, and a metal-first course of through which metallic is deposited earlier than the semiconductor is patterned.

Within the lift-off samples, the researchers noticed a skinny, patchy layer of carbon between the metallic and the semiconductor left over from photoresist supplies used throughout processing. To sort out the contamination, a one-hour UV-ozone publicity successfully eliminated the carbon layer, enabling a contact resistance as little as 0.05 ohm-millimeters, among the many lowest reported for non-alloyed beta gallium oxide contacts.

Carbon contamination ensuing from air publicity within the metal-first fabrication technique was remediated with a five-minute lively oxygen remedy, considerably decreasing the contact resistance and bettering present circulation.

“This analysis allows a solution to produce dependable, constant ultra-wide bandgap units,” Pieczulewski stated. “It is an incremental progress, however I feel it is vital when it comes to shifting towards commercialization.”

The research’s different co-lead writer is Kathleen Smith, Ph.D. ’24. Corresponding authors embody Huili Grace Xing, the William L. Quackenbush Professor of Electrical and Pc Engineering and of Supplies Science and Engineering; and David Muller, the Samuel B. Eckert Professor of Engineering within the Faculty of Utilized and Engineering Physics.

The research was the primary to unite on one analysis paper all seven co-principal investigators of the AFRL-Cornell Heart for Epitaxial Options, also called ACCESS, which together with Xing and Muller embody Debdeep Jena, the David E. Burr Professor of Engineering; Michael Thompson, the Dwight C. Baum Professor in Engineering; Darrell Schlom, the Tisch College Professor; Farhan Rana, the Joseph P. Ripley Professor of Engineering; and Hari Nair, assistant professor of supplies science and engineering.

Boise State College and Micron, by the Semiconductor Analysis Company (SRC), contributed superior characterization methods to the research.