Copper Oxide–Based MOS Capacitors for High-Frequency Applications

Abstract

Cu₂O is an important material for optoelectronics and communication technologies because of its suitable bandgap, strong light absorption, and potential for low-cost device fabrication. Improving its crystallinity is essential to reduce defects, enhance charge transport, and achieve better optical and electronic performance, leading to more efficient and reliable devices. Herein copper oxide thin films deposited onto glass and n-Si silicon substrates and partially recoated with molybdenum nanosheets are employed as high frequency metal-oxide-semiconductor (MOS) capacitors. Mo-coating improved the crystallinity and lowered the defect density in CuO.  Optically, Mo nanosheets widened the energy band gap without significant variation in absorption spectra of the glass/CuO films. The MOS capacitors displayed accumulation-depletion-inversion switching characteristics in the frequency domain of 1.0-100 MHz allowing for ultrafast charging/discharging cycle within 10 ns. In addition, Mo-coating lowered the built in potential and tuned the accumulation-inversion switching mode. Moreover, treating the MOS devices as high frequency bands filters in the range of 1.0 M- 6.0 GHz showed the ability of the devices to transmit/reject signals in three high frequency bands centered at 1.02 GHz, 1.47 GHz and 3.30 GHz. The ideal reflection coefficient values approaching zero, return loss characteristics exceeding -43 dB and voltage standing wave ratios (VSWR) equal 1.0 is obtained at notch frequency of 3.30 GHz. The bandwidth at this frequency reaches 2.0 GHz.  The features of the CuO-based MOS capacitors presented by ultrafast mode switching, high frequency filtering, wideband-frequency control, large values of return loss and ideality of VSWR nominate them for 6G technology applications.