The effect of annealing on the Sn-doped (−201) β-Ga2O3 bulk

Unintentionally-doped (UID) and Sn-doped crystals of (−201) β-GaO were high-temperature annealed in N and O atmospheres. Surface morphology and structure properties were investigated to quantify the effect of annealing process on the Sn-doped (−201) β-GaO bulk. The smooth step structure can be obtained on the surface of UID β-GaO bulk after annealing, which was absent for Sn-doped bulk. According to high-resolution X-ray diffraction (HRXRD), the crystal quality of Sn-doped GaO bulk was improved after annealing in O atmosphere. However, there was an obvious Sn segregation effect near the surface, detected by secondary ion mass spectrometry (SIMS), which may be responsible for the increase of surface roughness. In addition, the green luminescence (GL) of cathodoluminescence (CL) spectra, related to the gallium vacancies (V), were significantly enhanced for Sn-doped samples after 1100 °C annealing. And as the depth of penetration deepened, the ratio of GL to UV increased. It is shown that the formation of V-related defect is a dominant process for Sn-doped β-GaO bulk during high-temperature annealing.