Optimizing the Growth of Antimony Doped Sn₄₀Ge₆₀O₂ Thin Films

Rutile germanium dioxide has drawn a lot of attention due to its large bandgap, structural stability, and high thermal conductivity. Enhanced stability offered through alloying with tin dioxide makes these rutile structured oxides excellent candidates for next generation power electronic devices. Due to rutile oxides only recently being recognized as an ultra-wide bandgap semiconducting material, potential dopant and contact materials remain speculative. In this work, we confirm antimony as an effective dopant in single crystal SGO thin films grown on (10-10)-oriented sapphire substrates. Through variation of doping concentration from 0.03-3.3%, we identify lower and upper doping limits for thin films. Additionally, we are able achieve carrier densities of up to 1.7x10²⁰ cm^-3 and mobilities up to 33 cm²/Vs at room temperature. Notably, it is observed that germanium vacancies can act as electron sinks when in high concentrations drastically minimizing carrier mobilities and rendering films insulating. Our work establishes optimized conditions for synthesizing Sb-doped thin films using pulsed laser deposition and the interplay between electron transport and deposition conditions.