Interface characterization of atomic layer deposited high-k on non-polar GaN

The interface properties between dielectrics and semiconductors are crucial for electronic devices. In this work, we report the electrical characterization of the interface properties between atomic layer deposited Al₂O₃ and HfO₂ on non-polar a-plane (11 2 0) and m-plane (1 1 00) GaN grown by hybrid vapor phase epitaxy. A metal oxide semiconductor capacitor (MOSCAP) structure was used to evaluate the interface properties. The impact of annealing on the interface properties was also investigated. The border trap in the oxide, characterized by the capacitance-voltage (C-V) hysteresis loop, was low. The interface state density (D_it), extracted using the ac conductance method, is in the range of 0.5 × 10¹²/cm² eV to 7.5 × 10¹¹/cm² eV within an energy range from 0.2 eV to 0.5 eV below the conduction band minimum. The m-plane GaN MOSCAPs exhibited better interface properties than the a-plane GaN MOSCAPs after annealing. Without annealing, Al₂O₃ dielectrics had higher border trap density and interface state density compared to HfO₂ dielectrics. However, the annealing had different impacts on Al₂O₃ dielectrics as compared to HfO₂. Our results showed that the annealing degraded the quality of the interface in HfO₂, but it improved the quality of the interface in Al₂O₃ devices. The annealing also reduced the positive trapped oxide charge, resulting in a shift of C-V curves towards the positive bias region.