Passivation of H‐terminated diamond with MOCVD‐aluminium nitride – a key to understand and stabilize its surface conductivity

The surface conductivity of hydrogen (H)‐terminated diamond still suffers from instabilities at high temperature especially in O‐containing atmosphere and/or under high power FET device operation. For devices based on this H‐induced surface conductivity concept, stabilization is thus essential. In this investigation AlN, deposited by MOCVD at 800 °C, has been used as passivation and gate dielectric in Surface Channel MESFET and MISFET structures. Despite the high deposition temperature, the H‐induced channel is still present in the case of both structures and can be fully modulated. Surface Channel MESFETs yield a maximum output current density of 200 mA/mm (at pS = 9.5 × 1012 cm−2) in enhancement mode of operation. MISFETs display 20 mA/mm current density (at pS = 2.1 × 1012 cm−2) in semi‐enhancement mode of operation, the maximum current being limited by AlN dielectric breakdown. The film shows strong adhesion. To explain all features consistently, it is proposed that the interfacial bonding is provided by a H‐double bond.