Electro-optical dynamics in SnO2 designed as negative resistance sources and gigahertz/terahertz band filters

Abstract

Amorphous thin films of SnO2, prepared by a vacuum evaporation technique under a pressure of 10− 5 mbar, are employed as electro-optical filters suitable for microwave, infrared, and visible light communication technologies. The filters perform as optical layers, exhibiting optical transitions within an energy band gap of 3.62 eV, with the band gap containing energy band tails of widths of 0.63 eV. In addition, dielectric dispersion analyses on the optical filters show their ideality for high k-gate dielectric applications. Wide tunability in the dielectric response is observed in these films. Moreover, analyses of the optical conductivity and terahertz cutoff frequency spectra have shown that SnO2 films exhibit resonance of optical signals suitable for infrared and visible light communication technology as well. When excited with infrared light of energy of 1.38 eV, the drift mobility and free hole concentration in these films reach 11.72 cm2/Vs and 2 × 1017 cm− 3, respectively. Furthermore, the device exhibits a negative resistance effect in the microwave range of 0.1–1.80 GHz, and terahertz cutoff frequency values in the range of 10 GHz − 48 THz. The features of the SnO2 electro-optical band filter make them attractive for communication technology extending from 5G/6G to IR and reaching visible light communications.