Al₂O₃ Dielectric Layers on H-terminated Diamond: Controlling Surface Conductivity

Dielectric layers on H-terminated diamond have enabled recent breakthroughs in high voltage and high temperature FET operation. This study investigates how the surface conductivity of H-terminated diamond can be preserved and stabilized by using a dielectric layer with an in situ post-deposition treatment. Thin Al₂O₃ layers were grown by PEALD on H-terminated undoped diamond (100) surfaces. The changes of the hole accumulation layer were monitored by correlating the binding energy of the diamond C 1s core level with electrical measurements. The initial Al₂O₃ PEALD resulted in an increase of the C 1s core level binding energy consistent with a reduction of surface conductivity. A hydrogen plasma step restored the C 1s binding energy and the diamond surface resistance within the range for surface transfer doping. Further PEALD growth did not appear to degrade the surface conductive layer according to the position of the C 1s core level and electrical measurements. This work provides insight into approaches to establish and control the two-dimensional hole-accumulation layer of H-terminated diamond and improve the stability and performance of H-terminated diamond electronic devices.