Defect regulation of AlN films based on Al-rich AlN targets

Abstract

Aluminum nitride (AlN) films with low defect concentration were fabricated on Si substrates via RF magnetron sputtering system based on Al-rich AlN (Al-AlN) targets. The effects of Al-rich content on structure, defects and photoelectric properties of AlN films were investigated by x-ray diffraction (XRD), high resolution transmission electron microscopy, x-ray photoelectron spectroscopy (XPS), low temperature photoluminescence (PL), ultraviolet-visible spectra, current–voltage (I–V) and capacitance–voltage (C–V) characteristics. In particular, the defects of AlN films were investigated by XPS and low-temperature PL analyses, indicating that Al-rich AlN targets can help to reduce the defects of Al vacancy and O impurity of AlN films with an optimal Al-rich content of 1.5 wt. % (A1.5). Schottky contact behavior between AlN films and Ti/Al/Ni/Au multi-layer electrodes were revealed from I–V curves of all samples based on parallel electrodes, and AlN metal-semiconductor-metal (MSM) devices prepared by A1.5 films exhibited the lowest leakage current of 2.43 × 10−8 A at the bias of 5 V. C–V tests indicate the less defect density and lower carrier concentrations of vertical structure of A1.5 devices. This work offers a feasible approach to regulate the defects of AlN films for practical application.