Improving Doping Efficiency of Mist-CVD Epitaxy for Tin-Doped α-Ga₂O₃ Using Tin Chloride Pentahydrate

Abstract

Tin chloride pentahydrate (SnCl ${_{{4}}} \cdot 5$ H2O) is used as the dopant precursor to form the n-type $\alpha $ -Ga2O3 in this study. The X-ray diffraction (XRD) and high-resolution transmission electron microscope (HR-TEM) confirm that the single-crystalline $\alpha $ -Ga2O3:SnCl ${_{{4}}} \cdot 5$ H2O epi-layer was grown on the r-plane sapphire substrate using mist chemical vapor deposition (mist-CVD). When the Sn doping atomic concentrations are the same, the electron concentration of $\alpha $ -Ga2O3:SnCl ${_{{4}}} \cdot 5$ H2O is higher than that of $\alpha $ -Ga2O3:SnCl ${_{{2}}} \cdot 2$ H2O. The lower thermal decomposition temperature and lower residues of $\alpha $ -Ga2O3:SnCl ${_{{4}}} \cdot 5$ H2O are confirmed in thermogravimetric (TGA) analysis. Sn $3d_{5/2}$ binding energy spectra observed by X-ray photoelectron spectroscopy (XPS) show that SnCl ${_{{4}}} \cdot 5$ H2O provides more $Sn^{4+}$ than SnCl ${_{{2}}} \cdot 2$ H2O. The specific contact resistivity of $\alpha $ -Ga2O3:SnCl ${_{{4}}} \cdot 5$ H2O reaches $1.62\times 10{^{-}5 }~\Omega $ -cm2 with $10^{20}$ cm $^{-}3 $ Sn doping concentration. Moreover, the power figure-of-merit (PFoM) of $\alpha $ -Ga2O3:SnCl ${_{{4}}} \cdot 5$ H2O-based lateral Schottky barrier diode (SBD) is 0.356 GW/cm2 which is comparable to $\beta $ -Ga2O3-based SBD.