Diodes are very important components in modern electronics and act like one-way valves for electricity. They allow current to flow in only one direction, while blocking it in the other, which makes them crucial for converting AC to DC, protecting circuits from power surges, and ensuring signals move correctly in devices like power supplies, radios, and LED lighting.

Regular Diodes Are Inefficient

Traditional diodes use a "p-n junction," where two semiconductor materials—one with extra electrons (n-type) and one with missing electrons (p-type)—create a barrier that controls electricity flow. But they can be inefficient: traditional diodes lose energy as heat and operate more slowly in high-speed applications.

_… Schottky Barrier Diodes Bring Advantages

Schottky Barrier Diodes (SBD), however, are able to deliver better performance by using a metal-semiconductor junction instead of a p-n junction. This reduces electrical resistance, speeds up switching, and lowers energy loss, which makes SBDs perfect for high-speed and high-efficiency applications.

And Aluminum Nitride Helps

Schottky Barrier Diodes are not new—they've been used in electronics for decades—but recent advancements in Aluminum Nitride (AlN)-based SBDs, developed by NTT in collaboration with the University of Tokyo, have the potential to produce big improvements. AlN, an ultra-wide bandgap semiconductor, can handle much higher voltages and temperatures than traditional materials.

Schottky Barrier Diodes, first theorized by German physicist Walter Schottky in the early 1900s and practically developed in the mid-20th century, use metal instead of a semiconductor junction. This gives them faster switching and lower power loss. And now the development of AlN-based SBDs mean they're an even better option.

Wide Bandgap For High Power and Thermal Stability

AlN needs 6.0 electron volts (eV) of energy to make its electrons move and conduct electricity. This is a comparatively large bandgap, which means it can operate under extreme electrical stress while still maintaining high efficiency. A bandgap is the amount of energy needed to move an electron within a semiconductor; a wider bandgap allows a device to operate at higher voltages. This makes AlN ideal for applications that need both high power and thermal stability, such as electric vehicle chargers, industrial power converters, and renewable energy inverters.

One of the main difficulties of using AlN for power electronics until now has been making electrical connections with low levels of resistance. When resistance is high, efficiency drops, and excess heat is produced, which wastes energy.

NTT's researchers have found a way to create low-resistance connections. They have also reduced leakage current—small amounts of unwanted electricity that escape when the diode should be blocking it—bringing SBD performance close to perfect.

Thermionic Field Emission Efficiencies

For its part, the University of Tokyo studied how electricity moves through these AlN-based SBDs. They found that electrons can pass through the Schottky barrier more easily due to a process called thermionic field emission (TFE), which is where heat and an electric field help electrons move through a barrier more easily. Their research also measured how the barrier behaves at different temperatures, which is important for designing better semiconductor devices.

What does this research mean for you and me? NTT and the University of Tokyo's work could benefit a number of major industries:

Electric Vehicles and Charging Infrastructure: AlN-based SBDs could lead to smaller, more efficient EV chargers and power converters, reducing energy loss and heat generation. Look forward to faster charging times and longer-lasting components in EV power systems.

Renewable Energy and Power Grids: In solar and wind energy systems, AlN-based diodes could improve power conversion efficiency, meaning that more of the generated electricity is used rather than lost as heat. Making renewable energy systems more reliable and cost-effective.

High-Power Industrial Electronics: Industries like aerospace, manufacturing, and high-voltage power systems require components that can withstand extreme conditions. The high-temperature stability of AlN makes it ideal for those conditions, reducing the need for cooling systems and increasing reliability.

Thanks to NTT and the University of Tokyo, AlN-based Schottky diodes are a step closer to real-world use and we can expect lower energy consumption and more efficient power systems, supporting industries in creating a cleaner, more sustainable future.

NTT—Innovating the Future

Daniel O'Connor

Daniel O'Connor joined the NTT Group in 1999 when he began work as the Public Relations Manager of NTT Europe. While in London, he liaised with the local press, created the company's intranet site, wrote technical copy for industry magazines and managed exhibition stands from initial design to finished displays.

Later seconded to the headquarters of NTT Communications in Tokyo, he contributed to the company's first-ever winning of global telecoms awards and the digitalisation of internal company information exchange.

Since 2015 Daniel has created content for the Group's Global Leadership Institute, the One NTT Network and is currently working with NTT R&D teams to grow public understanding of the cutting-edge research undertaken by the NTT Group.