Charge trapping at Fe due to midgap levels in Ga2O3

Abstract

Fe acts as an electron trap in gallium oxide (Ga2O3), thereby producing a semi-insulating material that can be used in device fabrication. However, such trapping can lead to negative effects when Fe is unintentionally incorporated into bulk crystals or thin films. In this work, photoinduced electron paramagnetic resonance (photo-EPR) is used to investigate carrier capture at Fe in β-Ga2O3. Two crystals doped with 8 × 1017 cm-3 and 5 × 1018 cm-3 Fe and one Mg-doped crystal containing 7 × 1016 cm-3 unintentional Fe are studied by illuminating with LEDs of photon energies 0.7-4.7 eV. Steady state photo-EPR results show that electrons excited from Ir, an unintentional impurity in bulk crystals, are trapped at Fe during illumination with photon energy greater than 2 eV. Significantly, however, trapping at Fe also occurs in the crystals where Ir does not participate. In such cases, we suggest that excitation of intrinsic defects such as oxygen or gallium vacancies are responsible for trapping of carriers at Fe. The results imply that the investigation of intrinsic defects and their interaction with Fe is necessary to realize stable and reliable Ga2O3:Fe devices.