Interfacial GaO_x in $\text{Al}_{2}\mathrm{O}_{3}/n-\text{GaN}$ MOS Structures Studied by Quasi-Static CV and ToF-SIMS

Wide-bandgap MOS devices are prone to bulk dielectric charge defects and interface trapping defects related to weak or dangling bonds and contaminates at/near the insulator-semiconductor interface. This is especially true for GaN-based devices that rely on deposition techniques like atomic layer deposition (ALD) to form gate and passivation dielectrics. This work studies the impacts of interfacial GaO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> on the capacitive signature of ALD-Al2O3/n-GaN MOS capacitors using a relative quasi-static capacitance-voltage (QS-CV) methodology that circumvents the sources of error reported in other QS-CV methods. Time-of-flight secondary ion mass spectrometry shows that a thicker GaO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> interlayer is associated with a hump-like feature in the QS-CV response. Initial assessment suggests that greater amounts of interfacial GaO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> correlate with a greater density of interface trapping states deeper in the bandgap. However, a parallel capacitor model that considers laterally inhomogeneous bulk dielectric charge densities shows that a non-uniform surface potential may also be present.