Design and Characterization of the Ge/Ga₂S₃ Heterojunction

Abstract

In this work, the formation and properties of Ga₂S₃ thin films deposited onto polycrystalline Ge substrates are studied by means of scanning electron microscopy, energy dispersive x-ray analyzer, Raman spectroscopy, x-ray diffraction techniques, ultraviolet–visible light spectrophotometry in the range of 300–1100 nm and by ac signal power spectroscopy in the range of 0.2–3.0 GHz. The first four techniques allowed the determining of the stoichiometry, the vibrational frequencies, the lattice parameters, the plane orientations, the strain and the defect density for the interface. In addition, it was observed that the Ge/Ga₂S₃ interface exhibited conduction and valence band offsets of 0.83 eV and 0.82 eV, respectively, and the real part of the dielectric spectra experimentally exhibited four resonance peaks centered at frequencies above 357 THz. Moreover, the computational analysis of the imaginary part of the dielectric constant via the Drude–Lorentz model has shown that the interface wave filtering properties are controlled by the electron–plasmon coupling with plasma frequencies in the range of 1.33–2.30 GHz. The drift mobility of electrons in this range was found to be 15.61 cm²/Vs. The real ability of the interface to control wave propagation was confirmed with ac signals propagating tests. The plasmonic features of the interface nominate it for use in microwave cavities and as wireless terahertz receivers.