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Compound Semiconductor Research in the Fast Lane


Ryann Monahan, Illinois ECE

Can Bayram
Can Bayram

An Illinois ECE research team is putting compound semiconductor research in the fast lane, setting the stage for significant strides in the industry that has wide-reaching impact on modern technologies. The impact will include switching to solid-state lighting for halving our lighting electricity usage, 5G communication for networked devices, and solar and wind farms for energy.

Semiconductors are microscopic technologies that come with massive power.  They are utilized in nearly all aspects of modern technologies - from lighting to communication and computing transportation, we rely on semiconductors for comfort, safety, and sustainability. 

However, the 21st century is the age of compound semiconductors.  Although the compound semiconductor industry currently represents about 10 % of the total semiconductor revenues worldwide, it is also growing 50% faster than the semiconductor industry overall. 

 “Our reliance on elemental semiconductors is to evolve into compound ones as solid-state lighting extends into horticulture and medicine, new communication spectra above 95 gigahertz open opportunities for 6G and beyond networking, and adoption of renewable power sources revolutionize electric grids,” Can Bayram, professor of Electrical and Computer Engineering at the University of Illinois at Urbana-Champaign explained.

Bayram and his research team are leading the research through the world of compound III-V semiconductors. The team is working to understand, control, and exploit III-V semiconductor technologies and create an innovative research platform considering the needs of not only the current but also of the next generation.

“Our current goal is to mass manufacture and commercialize the core technology platform of cubic GaN for advanced photonics (e.g. solid-state lighting) and electronics (e.g. wide bandgap logic functions),” Bayram said.

Compared to competing technologies, Professor Bayram’s cubic-phase GaN platform offers a lower density of defects, which converts into increased light emission efficiency, greater operating lifetime, greater temperature operating range, and lower cost for next-generation solid-state lighting. 

“This platform might also enable GaN-based logic circuitry, which is extremely important for the future of high-power, high-voltage, high-temperature RF and power transistors because it is compatible with the existing silicon substrate platform, saves energy, and brings additional capabilities to the silicon-dominated transistor world,” Bayram said.

At Illinois, Prof. Bayram and his team proved using first-principles calculations the material advantages of c-phase III-nitrides over h-phase III-nitrides {Sci. Rep.  9:6583 (2019)}, validated his theoretical modeling in growing single-phase low-defectivity c-phase III-nitrides {Appl. Phys. Lett. 109, 042103 (2016)}, patented the phase-transition via U-groove technique {U.S. Patent 10,027,086}, experimentally demonstrated high-efficiency (~29%) room-temperature optical emission from c-phase GaN {ACS Photonics 5 (3), 955–963 (2018)}, and theoretically studied and patented complementary logic circuits based on cubic GaN transistors {J. Phys. D: Appl. Phys. 50, 265104 (2017)U.S. Patent 10,211,328}.

The team’s latest work {ACS Omega 5, 3917 – 3923  (2020)}, led by Bayram and Illinois ECE graduate student Yi-Chia, reveals cubic III-nitride semiconductor properties and provides further evidence to why cubic III-nitrides are the future of photonic and electronic devices.

“We report, for the first time, bandgaps, electron affinities, and band alignments of wz- and zb- III-nitrides using a unified HSE06 hybrid functional, while the mixing parameters are calibrated from the experimental bandgap of binary wz- III-nitrides. The band diagrams of III-nitrides are aligned using Anderson’s electron-affinity model. The bandgap bowing in wz- and zb- III-nitrides is dominantly contributed from the nonlinear dependence of conduction band offset on compositions,” Bayram explained.

“We found that the large bowing of conduction band offsets is attributed to the cation-like conduction band minimum at Γ-valley; whereas, the linear dependence of valence band offsets is ascribed to the anion character of the valence band maximum. Our work reveals fundamental advantages of zb- heterostructures over the wz- ones: Polarization-free nature, higher radiative efficiency, and less heat generation,” Chia explained.

This work was recently featured and made the cover of ACS Omega, a peer-reviewed journal published by the American Chemical Society. The cover art illustrates the crystal structure and band alignments of zincblende AlN/GaN/InN heterostructures. The innovative zincblende III-nitrides material system featuring type-I band alignment and polarization-free nature is beneficial to capture both electrons and holes for recombination and has broad emission wavelength ranging from ultraviolet, blue, green, to red spectrum.

Because of the unique properties of the compound III-V semiconductors, they have been the source of a rich world of science, technology, and applications. This world has led to 9 Nobel Prizes in Physics and created a roughly $40B global market in 2018 with a compound annual growth rate of 17.3%. 

Academia is the frontier research partner for industry and Illinois ECE researchers like Prof. Can Bayram are leading the way in this field. Illinois ECE has a vertically-integrated research infrastructure and an intra- and inter-departmental collaboration culture. All facilities, from simulation and growth to characterization and fabrication, are located within minutes of the Nick Holonyak Jr., Micro and Nanotechnology Laboratory. 

“Combined with 100+ world-class faculty and 2,500+ genius students, compound semiconductor research can take the fast lane in Illinois ECE, enabling students to be bold in science and leaders in technology.”

Bayram is also affiliated with the HMNTL.