Design and characterization of ZnSe/GeO${}_2$ heterojunctions as bandstop filters and negative capacitance devices

Herein, polycrystalline films of ZnSe which are coated onto Au substrates and recoated with amorphous layers of GeO${}_2$ are used as active material to perform as bandstop filters. The stacked layers of Au/ZnSe/GeO${}_2$ are coated under pressure of 10${}^{-5}$ mbar. The device is characterized by X-ray diffraction, X-ray photoelectron, X-ray fluorescence, and impedance spectroscopy techniques. It is observed that when the device is contacted with carbon point contacts, it exhibits resonance-antiresonance phenomena near 1.0 GHz. The Au/ZnSe/GeO${}_2$/C devices display negative capacitance effect in the frequency domain of 0.96-1.80 GHz. Analyses of the conductivity and capacitance spectra in the frequency domain of 0.01-1.80 GHz reveal the domination of conduction by quantum mechanical tunneling below 0.58 GHz and by the correlated barriers hopping above 0.58 GHz. In addition, characterizations of the impedance, reflection coefficient, return loss (L${}_r$) and voltage standing wave ratios (VSWRs) spectra of the device indicated ideal bandstop filter features. The notch frequency of the filter is 1.56 GHz. At this critical frequency, the Au/ZnSe/GeO${}_2$/C devices display ideal characteristics presented by VSWR of 1.0, L${}_r$ value of 28.9 dB. These features make the Au/ZnSe/GeO${}_2$/C heterojunction devices promising for use in telecommunication technology. (© 2021 Wiley‐VCH GmbH)