New fabrication processes for buried p+-type diamond using etching techniques based on the solid-solution reaction of carbon with nickel were proposed and demonstrated. Specifically, an inversion-channel diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) with source and drain regions buried in the body were fabricated, and their operation were confirmed. An etching process using etching techniques based on the solid-solution reaction of carbon with nickel was applied to realize trench formation and planarization after the growth of a p+-type diamond. The fabricated MOSFET exhibited drain current density equivalent to that of conventional MOSFET with source and drain p+-type regions deposited as islands on an n-type body, and ideal field-effect transistor characteristics with linear and saturation regions, and the drain current density was controlled by the gate voltage. However, the surface protrusion structure owing to the incomplete planarization process limited the device characteristics. The proposed fabrication processes for buried layers are expected to function as an important selective doping technique for diamond electronic devices such as ion implantation.
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