Diamonds, although not conductive, can be altered to function as semiconductors with the addition of phosphorus and boron. Silicon, the most common semiconductor, is widely used in memory devices and microprocessors. It is also used in power devices. Because power devices are key to the social infrastructure that facilitates smart grids, great capacity is required. As a result, the demand for high capacity energy production with minimal losses during power conversion requires the development of new semiconductor materials.
The thermal conductivity of the diamonds is 14 times greater than that of silicon, and the resistance of the electric field is 30 times greater. The high thermal conductivity allows the release of heat, which can reduce the size of cooling systems that are normally required during the generation of higher levels of electrical energy. The high electric field strength suppresses energy conversion losses. With these characteristics, diamonds are the latest semiconductors for electronic devices requiring several kilovolts (kV) of power, such as those used in electric vehicles, railways and power transmission.
Although the formation of diamond-based n-type semiconductors whose conducting carriers are electrons and p-type semiconductors whose conducting carriers are electron holes have been achieved, the difficulty has traditionally remained in the formation of the lateral pn junction , which is the basic structure of the devices. Collaborating with researchers from the National Institute of Advanced Industrial Science and Technology, Hatano established a p-n lateral junction, which was then applied to a prototype FET transistor. This was the world's first high-voltage power device whose application to power supply optimization in smart grids is significantly reducing environmental impact.