Thick crack-free {113} epitaxial boron-doped diamond layers for power electronics—Deposition with nitrogen addition and high microwave power

In this work, first, we investigate the effect of nitrogen addition in microwave plasma enhanced chemical vapor deposition on the growth of thick {113} epitaxial diamond layers. We identify a narrow range of nitrogen concentrations for the growth of crack-free thick epitaxial layers with a smooth surface morphology. Without nitrogen, cracks start to appear after a layer thickness of 7–10 μm due to elastic energy stored in the epitaxial layer, but the addition of nitrogen stabilizes layer growth. We also investigate the use of low microwave power density growth conditions to produce thick boron-doped epitaxial layers. We observe a very high boron incorporation efficiency using these growth conditions. Finally, we demonstrate the fabrication of a thick (>200 μm) {113} p+ monocrystal plate. The concentration of boron in heavily doped diamond with metallic conductivity has been investigated by the Hall effect measurement technique, Raman spectroscopy, and secondary ion mass spectroscopy. The growth of high quality thick {113} oriented epitaxial layer with high boron concentration (>1020 cm−3) and low resistivity and the fabrication for the freestanding p+ substrates are necessary steps for the fabrication of vertical electronic devices such as high power Schottky diodes.