Abstract
The effects of different post-deposition annealing ambients (oxygen, argon, forming gas (95% N2 + 5% H2), and nitrogen) on radio frequency magnetron-sputtered yttrium oxide (Y2O3) films on n-type gallium nitride (GaN) substrate were studied in this work. X-ray photoelectron spectroscopy was utilized to extract the bandgap of Y2O3 and interfacial layer as well as establishing the energy band alignment of Y2O3/interfacial layer/GaN structure. Three different structures of energy band alignment were obtained, and the change of band alignment influenced leakage current density-electrical breakdown field characteristics of the samples subjected to different post-deposition annealing ambients. Of these investigated samples, ability of the sample annealed in O2 ambient to withstand the highest electric breakdown field (approximately 6.6 MV/cm) at 10−6 A/cm2 was related to the largest conduction band offset of interfacial layer/GaN (3.77 eV) and barrier height (3.72 eV).
Highlights
Increasing concerns regarding the escalating demand of energy consumption throughout the world has triggered the needs of developing energy-efficient highpower and high-temperature metal-oxide-semiconductor (MOS)-based devices
The presence of oxygen-related defects, changes in compositional homogeneity of Y2O3, and formation of interfacial layer (IL) are of particular concern as either of these factors might alter the bandgap of Y2O3 and band alignment of Y2O3 with respect to the gallium nitride (GaN), which would influence the J-E characteristic of the MOS structure
The extracted Eg values are in the range of 4.07 to 4.97 eV and 1.17 to 3.93 eV with a tolerance of 0.05 eV for Y2O3 and IL, respectively, for samples annealed in different postdeposition annealing ambients (Figure 3a)
Summary
Increasing concerns regarding the escalating demand of energy consumption throughout the world has triggered the needs of developing energy-efficient highpower and high-temperature metal-oxide-semiconductor (MOS)-based devices. Native oxide (Ga2O3) of GaN [9,10,11,12,13] and a relatively lowdielectric-constant (k) SiNxOy [2] or SiO2 [14,15,16,17,18,19] have been successfully grown and deposited, respectively, as gate oxides in GaN-based MOS devices. These gate oxides are not the preferred choices. A correlation on the bandgap of Y2O3 gate and band alignment of Y2O3/GaN with regard to the J-E characteristics is discussed in this paper
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