Integration of High-κ and Ultrawide Bandgap Single-Crystalline Beryllium Borate Dielectric for 2D Electronics

The development of van der Waals (vdW) dielectric materials with high dielectric constants and wide bandgaps is crucial for advancing the practical application of two-dimensional (2D) transistors. However, current dielectrics often exhibit advantages in only one of these two aspects, which limits the further improvement of transistor performance. This study demonstrates an ideal dielectric NH₄Be₂BO₃F₂ (ABBF) for 2D electronic devices, which exhibit a high dielectric constant up to 39 and a wide bandgap of 8.1 eV. Dielectric performance tests show that it has an ultralow leakage current density (≈ 10^-8 A cm^-2) and a robust breakdown field (12.6 MV cm^-1). The MoS₂ field-effect transistors (FETs) gated by ABBF achieve a high on/off ratio of 2 × 10⁹, near-Boltzmann-limit subthreshold swing (60 mV dec^-1), and negligible hysteresis of 2.7 mV. Benefiting from its inert vdW surface, ABBF forms a high-quality MoS₂/ABBF interface with an extremely low density of trap states (D_it ≈ 4.6 × 10¹⁰ cm^-2 eV^-1). In addition, high-κ ABBF dielectrics were also applied for fabricating short-channel MoS₂ FETs and high-gain logic inverters. This research enlarges the pool of dielectric candidates and unlocks new possibilities for advancing low-power electronics and integrated circuits.