Dynamic effects of incomplete ionization in edge terminations of diamond power devices

The transient response of junction termination extensions (JTEs) in diamond-based Schottky diodes is critically influenced by the incomplete ionization of dopants under high electric fields and fast-switching conditions. Using an extended TCAD simulation framework that includes time-dependent ionization kinetics, we demonstrate that the limited ionization speed of phosphorus donors under fast voltage ramps leads to transient JTE charge reduction. This, in turn, degrades field management at the device edge and triggers premature avalanche breakdown, significantly reducing the effectiveness of conventional JTE structures. To address this limitation, we propose a hybrid edge termination approach that integrates phosphorus-doped JTEs with oxide field plates. This design maintains high termination efficiency under slow switching conditions while substantially restoring field control during fast transients, improving robustness across a wide operational range. Our findings underline the importance of accounting for dynamic ionization effects in the design of ideal edge terminations for diamond-based power devices, similar to observations in other wide-bandgap semiconductors.