Trap States in HfO₂/Ga₂O₃ and Al₂O₃/Ga₂O₃ Metal Insulator Semiconductor Structures

HfO 2 /(010) bulk Ga 2 O 3 and HfO 2 /(001) epi layer Ga 2 O 3 metal insulator semiconductor (MIS) structures were prepared by atomic layer deposition of HfO 2 at 300 °C with subsequent annealing at 500 °C. In addition, Al 2 O 3 /(001) epilayer Ga 2 O 3 MIS were also fabricated by e-beam deposition at room temperature. The structures were characterized by capacitance–voltage C – V and current–voltage I – V measurements in the dark and with monochromatic photoexcitation in the spectral range 1.3–4.5 eV and by deep level transient spectroscopy (DLTS). DLTS spectra measurements revealed the presence of interface states with the density D it peaking near E c -0.5 eV at 8 × 10 10 cm –2 eV –1 in HfO 2 MIS structures and D it peaking near E c -1.24 eV at a density of 1.1 × 10 12 cm –2 eV –1 in Al 2 O 3 MIS structures. For both dielectrics, a high density of border trap-related charge of ∼10 13 cm –2 was detected by C – V measurements with illumination. DLTS measurements are useful in the characterization of interfacial states in Ga 2 O 3 MIS with high leakage current in accumulation, for which standard C – V based techniques present problems.