Interface trap evaluation of Pd/Al2O3/GaN metal oxide semiconductor capacitors and the influence of near-interface hydrogen

Three interface state density (Dit) characterization methods to evaluate the oxide-semiconductor interface on metal-oxide-semiconductor capacitors fabricated on GaN are compared and discussed. Capacitance-voltage, conductance-voltage, and constant capacitance deep level transient and optical spectroscopy measurements are used to evaluate Dit at the Al2O3/GaN interface. The effect of annealing ambient on the Pd/Al2O3/GaN capacitors is also examined. Forming gas annealing reduces Dit; nitrogen annealing increases Dit for the annealing conditions tested. The Dit variation correlates with changes in hydrogen concentration at the Al2O3/GaN interface detected by secondary ion mass spectrometry suggesting that hydrogen plays an important role passivating Al2O3/GaN interfaces.