Electronic Applications of Diamond wafer

Silicon is a well-established semiconductor material that has addressed the requirements of energy conversion for more than 50 years. However, it is widely recognized that a real step improvement in power electronics will be obtained by employing devices based on wide band-gap semiconductor materials. Higher voltage capability devices are then highly required, 15 kV being a first step. To reach a high level current, paralleling of devices is required. Power electronic devices based on wide band-gap semiconductors are now resulting in substantial improvements in the performance of power electronics systems by offering higher blocking voltages, improved efficiency and reliability (higher performance/cost ratio), easier paralleling, and reduced thermal requirements, thus leading to the realization of more efficient green electronic systems.

Among wide band-gap semiconductors, diamond is considered to be the ultimate semiconductor for applications in high-power electronics due to its exceptional properties. Its dielectric breakdown strength is three times higher than in silicon carbide (SiC) and more than 30 times higher than in silicon (Si). In addition, unlike most other wide band-gap semiconductors, the carrier mobility is very high for both carrier types, and the thermal conductivity is unsurpassed. In the latter, we indicate the commonly reported values of mobilities measured by Hall bars set-ups on microwave-plasma-assisted chemical vapor deposition (MPCVD) layers. Power device engineering is interested in minimising the on-resistance for a given breakdown voltage capability. Diamond is the best candidate, and even Ga2O3, despite its lower carrier mobility, is better than SiC and GaN thanks to its high critical electric field.

Table1 Diamond's properties are strikingly superior to other semiconductors when considered for use in power electronic devices.

Figure1 ON-resistance and breakdown voltage of the different semiconductors at room temperature.

An important aspect to rise is that Si power semiconductor switches used in 90% of the power applications market are metal-oxide semiconductor(MOS) gate-controlled devices. Thyristor-based structures are still used for high-power high-voltage applications, mainly because of the lack of equivalent performance MOS controlled devices. This is something that diamond could solve considering its very high breakdown field above 10 MV/cm. Diamond, as a material with exceptional properties, could provide solutions to industry by providing diodes and transistors that withstand voltages above 10 kV. In general, WBG semiconductors like diamond could open the way to novel concepts and applications in the high-voltage field such as electric transport and energy generation and distribution.

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