Deep-level defects and carrier manipulation in Sn-doped β-Ga2O3 (100) single crystals
Defect engineering is pivotal in comprehending physical mechanisms that govern carrier transport and device performance. The defect evolution and carrier manipulation in Sn-doped Ga2O3 bulk crystals subjected to different thermal treatments were investigated, utilizing depth-profiled deep-level transient spectroscopy (DLTS) and frequency-dependent capacitance-voltage (C-V-f) techniques. In untreated Sn-doped Ga2O3 with an electron concentration of 6.37×10^17 cm^-3, two dominant electron traps, ET1 (EC−0.68 eV) and ET2 (EC−0.76 eV), were identified, corresponding to gallium vacancy (VGa) and the neutral complex of VGa-VO, respectively, and characterized as bulk traps. FeGa-related defects, ET3 (EC−0.84 eV), were concentrated near surface. Nitrogen annealing significantly reduced ET1, increased ET2 density from 6.13×10^15 to 1.1×10^16 cm^-3, and raised the interfacial state density (Dit) to 3.36×10^15 eV^-1 cm^-2, accompanied by an elevated electron concentration of 7.48×10^18 cm^-3. In contrast, air annealing enhanced ET1, with a density of 1.42×10^16 cm^-3, suppressed of ET2/ET3 traps, resulting in a lower Dit of 1.74×10^14 eV^-1 cm^-2, and a reduced electron concentration to 3.01×10^16 cm^-3. The findings reveal that a reducing environment induces VO formation and converts discrete VGa acceptors into neutral VGa-VO complexes, leading to downward surface band bending and electron accumulation. Conversely, VGa-VO complexes are dissociated into VGa acceptors in oxidizing conditions, leading to an upward surface band bending and electron compensation. This work underscores the carrier concentration manipulation by defect engineering in Ga2O3, offering insights essential for developing high-performance gallium oxide electronics.