Effects of annealing on the interfacial properties and energy-band alignment of AlN dielectric on 4H–SiC
Zhanwei Shen, Feng Zhang, Jun Chen, Zhao Fu, Xingfang Liu, Guoguo Yan, Bowen Lv, Yinshu Wang, Lei Wang, Wanshun Zhao, Guosheng Sun, Yiping Zeng
Abstract
Interfacial properties and energy-band alignment of annealed AlN dielectric films on Si-face 4° off-axis 4H–SiC substrates were characterized and demonstrated by x-ray photoelectron spectroscopy (XPS) and current-electric field (I–E) measurements. The XPS results reveal that the Al–O bonds and the silicon suboxides can convert into more stable Al–N bonds and Al–O–Si bonds at the AlN/4H–SiC interface under 1000 °C annealing. The variations in both oxygen-rich composition and the crystallinity in AlN make annealing-dependent conduction band offsets of as-deposited and annealed AlN/4H–SiC to be 1.36 eV and 1.20 eV, respectively. Meanwhile, I–E measurements separately yield the occurrence of the Fowler–Nordheim (FN) tunneling and space-charge-limited conduction in as-deposited and annealed metal-insulator-semiconductor capacitors, corresponding to lower barrier heights of 0.92 eV and 0.54 eV, respectively. The reason for the energy-band shift between I–E derivations and the XPS results was analyzed and demonstrated together. These results can provide considerable insight into the energy-band alignment of AlN as gate dielectric or passivation layers on 4H–SiC based devices.