Thermal Stabilization of Hole Channel on H-Terminated Diamond Surface by Using Atomic-Layer-Deposited Al₂O₃ Overlayer and its Electric Properties

We have established an atomic-layer-deposited Al 2 O 3 overlayer deposition method, which makes the H-surface-terminated p-type channel diamond surface thermally stable and completely keeps the concentration and mobility high even at 150 °C. In a range from 230 to 500 K, the mobility is proportional to the inverse of temperature showing a property characteristic for degenerate hole gas. The ionization energy is estimated to be 6.1 meV, indicating that holes are not generated mainly by thermal activation. This thermal stabilization technology enables us to measure hole properties up to 230 °C and to realize H-terminated diamond field-effect transistors with a reproducible high drain current.