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-Ga 2 O 3 ) 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/cm 2 ), high operating speed (>20 MHz), and high endurance (>10 10 cycles). To validate practical utility, MoS 2 field-effect transistors gated by β-Ga 2 O 3 were fabricated, exhibiting a high on / off ratio (>10 6 ), 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-Ga 2 O 3 as a compelling high- k material for next-generation logic and memory devices.