Thick boron doped diamond single crystals for high power electronics

Switch Mode Power Supply (SMPS) is now widely used for the control and conversion of electric power from one watt to several megawatts. In this context, the synthesis and use of wide bandgap semiconductor materials having physical characteristics superior to silicon is essential. Due to its outstanding physical properties (thermal conductivity, breakdown voltage, carrier mobilities…), diamond is a very promising material. However the success of its use in power electronics mostly relies on our ability to provide carriers by doping the material in a controlled manner. In particular the growth of thick heavily boron doped material is an essential requirement to develop vertical components which should allow, as it will be shown by modeling, limiting the series resistance of the devices in their on-state. Deposition conditions required to obtain high growth rate, high quality and heavily boron-doped material by plasma assisted chemical vapour deposition (MPACVD) will be described. It will be shown in particular that high growth rate, high-quality material, which is obtained at high microwave power density, comes at the expense of the boron concentration, and a compromise must be found. Preliminary results on boron doping of single crystal diamond will be presented and associated with electrical properties of pseudo-vertical Schottky Barrier Diodes (SBD). In particular, a critical electric field of 1.3 MV/cm has been demonstrated with a rectifying ratio of 109. In the same time, current density close to 1500–2000 A cm− 2 has been reached, showing the potentiality of diamond for power-electronic applications.

Research Highlights
► We Model Schottky diodes and show the interest of developing vertical structures.
► Growth conditions to obtain thick heavily boron doped diamond have been determined.
► Schottky diodes with current density close to 1500 A.cm2 have been obtained.