Ultrahigh Dielectric Permittivity in Ultrathin 2D β-Ga 2 O 3 for Advanced Dielectric Applications

The continuous scaling of semiconductor devices necessitates the integration of high-permittivity (high-k) dielectrics to maintain gate control and reduce power consumption. Here, we report an ultrahigh dielectric constant (k) of ∼150 in ultrathin (10 nm) β-gallium oxide (β-Ga₂O₃) metal-insulator-metal capacitors. Photoresponse and microstructural analyses link the giant permittivity to an oxygen vacancy (V_O)-ordered phase. The fabricated capacitors exhibit excellent performance for memory applications, including low dielectric loss (<0.02 at 100 kHz), low leakage current (<10^-7 A/cm²), high operating speed (>20 MHz), and high endurance (>10¹⁰ cycles). To validate practical utility, MoS₂ field-effect transistors gated by β-Ga₂O₃ were fabricated, exhibiting a high on/off ratio (>10⁶), a low subthreshold swing (SS) of 68.1 mV/dec, negligible hysteresis (5.8 mV), and ultralow gate leakage (∼10^-13 A). These findings establish ultrathin β-Ga₂O₃ as a compelling high-k material for next-generation logic and memory devices.