Isotype n-Si/n-Bi2O3 Heterojunctions Designed as High-Frequency MOS Devices, Microwave Band Filters and Quad Band 5G/6G Antennas

Herein, a hybrid device structure is designed for high-frequency applications. The device is fabricated by the thermal evaporation of n-Bi₂O₃ nanosheets onto n-Si substrates to form an isotype heterojunction encapsulated between two Schottky barriers (Ag/n-Si, Pt/n-Bi₂O₃). The hybrid-structured device exhibits metal–oxide–semiconductor (MOS) characteristics that can be depleted in the frequency domain of 1–70 MHz. The complex device structure exhibits two identical flat-band built-in potentials with a value of 0.97 eV. MOS devices display a charging/discharging cycle within a time scale of 14.3 ns. In addition, when experimentally tested as band-pass/reject filters in the quad-band range of 0.01–1.80 GHz, the device shows a high cutoff frequency up to ~19 GHz at a quad frequency of 1.80 GHz. Moreover, when employed as a multiport 5G/6G antenna using a network analyzer working in the frequency domain of 1.0–6.0 GHz, the devices show promising antenna characteristics suitable for the targeted technology applications. Specifically, the measured reflection and transmission coefficient parameters for the two-port antenna designs show isolation parameters down to −24.5 dB. The features of the two-port antennas, which demonstrate good isolation between transmitted signals, are promising for use of the Ag/n-Si/n-Bi₂O₃/Pt hybrid devices in high-frequency networks including 5G/6G technology.