Deep-level defects and carrier manipulation in Sn-doped β-Ga2O3 (100) single crystals

• • Nitrogen annealing (reducing ambient) increases electron concentration from 6.37×10^17 cm^-3 to 7.48×10^18 cm^-3, a 11.7-fold rise, while raising interface state density (Dit) to 3.36×10^15 eV^-1 cm^-2; this enables degenerate n-type Ga2O3 for low-resistance Ohmic contacts, critical for reducing conduction losses in power switching devices. • • Air annealing (oxidizing ambient) reduces electron concentration to 3.01×10^16 cm^-3 and suppresses Dit to 1.74×10^14 eV^-1 cm^-2, a 19.3-fold reduction versus nitrogen-annealed samples; this yields a highly resistive layer suitable for current blocking layers (CBL) in vertical MOSFETs, directly addressing the need for enhancement-mode operation. • • The ET2 trap (VGa-VO complex) density increases from 6.13×10^15 to 1.1×10^16 cm^-3 after nitrogen annealing, while ET1 (VGa) is reduced; this defect transformation converts deep acceptors into neutral complexes, mitigating compensation and enabling controllable carrier concentration—essential for reproducible doping in Ga2O3 epitaxy. • • FeGa-related ET3 (EC−0.84 eV) is concentrated near the surface and its detectability is enhanced by nitrogen annealing due to Fermi-level-induced reduction of formation energy; air annealing suppresses ET3, demonstrating that thermal budget directly modulates unintentional Fe contamination, a key reliability concern for high-field devices.