Interface trap characterization of atomic layer deposition Al2O3/GaN metal-insulator-semiconductor capacitors using optically and thermally based deep level spectroscopies

Quantitative measurements of interface state density and energy distribution profiles within Al2O3/GaN interfaces were obtained by constant capacitance deep level transient spectroscopy and deep level optical spectroscopy (CC-DLTS/DLOS). The new application of CC-DLOS to interface state measurement is described, which allows interrogation of very deep interface states. A series of Al2O3/GaN metal-insulator-semiconductor (MIS) devices prepared as a function of Al2O3 thickness via atomic layer deposition, on NH3-MBE-grown n-type Ga-polar GaN layers enabled a systematic study. The overall shape and magnitude of the interface trap distribution, Dit, were determined to be nearly identical, independent of Al2O3 thickness. The Al2O3/GaN Dit spectra had an overall U-shape with Dit ∼1012 cm−2 eV−1 near the conduction band edge, ∼1011 cm−2 eV−1 mid-gap, and ∼1014 cm−2 eV−1 near the valence band edge. However, the interface states near the GaN conduction band showed a slight inverse dependence on Al2O3 thickness, su...

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