Akademik Veri Yönetim Sistemi
Journal of Applied Physics, cilt.113, sa.20, 2013 (SCI-Expanded)
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 Al 2O3 thickness via atomic layer deposition, on NH 3-MBE-grown n-type Ga-polar GaN layers enabled a systematic study. The overall shape and magnitude of the interface trap distribution, D it, were determined to be nearly identical, independent of Al 2O3 thickness. The Al2O3/GaN D it spectra had an overall U-shape with Dit ∼10 12 cm-2 eV-1 near the conduction band edge, ∼1011 cm-2 eV-1 mid-gap, and ∼10 14 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, suggestive of annealing effect during deposition. The high near valence band state concentrations are consistent with expectations from residual carbon impurities at the GaN surface. A method for discriminating between bulk and interface states in the CC-DLTS signal is demonstrated, using the results on MIS capacitors in combination with spectroscopy results on a Schottky diode structure. © 2013 AIP Publishing LLC.