Investigation of unintentional Fe incorporation in (010) β-Ga2O3 films grown by plasma-assisted molecular beam epitaxy

Transition metals, such as Fe, are commonly used in either layers or substrates to serve as deep intentional acceptors to realize semi-insulating substrates, regrowth interfaces, or buffer layers. The unintentional incorporation of the compensating acceptor in subsequent layers is a major concern in epitaxial growth. In this paper, we report on unintentional Fe incorporation for the homoepitaxial growth of (010) β-Ga2O3 by plasma-assisted molecular beam epitaxy on (010) Fe-doped β-Ga2O3 substrates. Fe was found to incorporate heavily into films grown at 500 °C, while growth temperatures of 650 °C and higher showed a significantly longer tail of Fe in the films. This Fe tail was determined to be a result of surface riding during growth rather than diffusion. The total surface riding concentration of Fe was found to be approximately 3 × 1012 cm−2 from a typical Fe-doped (010) β-Ga2O3 substrate. Surface segregation coefficients of 0.982 and 0.993 were calculated for growth temperatures of 500 °C and 700 °C, respectively. Furthermore, growth temperatures of 500 °C–700 °C demonstrated high crystalline quality and smooth surface morphology.