Japan-based Powdec has announced that together with Sheffield University, they have succeeded in developing breakthrough high-voltage GaN power transistors. This was realized by creating semiconductor hetero-junction structures based on novel principles, which solve the problems of conventional transistors and dramatically improve the transistor erformance.
Current collapse is almost completely eliminated, power losses are reduced and high break-down voltages of more than 1,100V are realized in the new transistors, Powdec said. These new GaN transistors are suited to be used in a broad range of equipment from inverters in consumer appliances to server power supplies, electric vehicles and industrial motors to lower power use.
Powdec revealed that in its breakthrough solution, instead of a conventional metal field plate, a thin film of p-type GaN (p-GaN) is used. The company succeeded in realizing a polarization effect in the top and bottom interfaces of the AlGaN (aluminium gallium nitride) layer where equal negative and positive charge is generated, creating a 2-dimensional hole gas (2DHG) and 2-dimensional electron gas (2DEG) at the interfaces. This polarization effect almost completely suppresses both the current collapse and current leakage at the gate of the HFET (heterojunction field effect transistors). This is a similar effect seen in silicon super junction devices where the entire length of the gate-drain channel is depleted (high resistance), and the electric field is distributed uniformly along the channel, enabling these GaN transistors to sustain high breakdown voltages.
Powdec solved the difficult issue of realizing a high hole density in collaboration with University of Sheffield. This allowed a 2DHG of high hole density to be achieved for the first time in the world, the company claimed.
Going forward, Powdec's breakthrough HFET technology can be easily combined with 'normally-off' structures. Powdec plans to shift growth of the devices to large diameter silicon wafers, with aims to have these energy efficient, high voltage products shipping in volume in two to three years. To accelerate the market adoption of these innovative, low-power GaN devices, Powdec said it is actively expanding its partnerships worldwide.
