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O vapor on GaN surfacesSumiya, Masatomo*; Sumita, Masato*; Tsuda, Yasutaka; Sakamoto, Tetsuya; Sang, L.*; Harada, Yoshitomo*; Yoshigoe, Akitaka
Science and Technology of Advanced Materials, 23(1), p.189 - 198, 2022/00
Times Cited Count：4 Percentile：51.62(Materials Science, Multidisciplinary)GaN is an attracting material for power-electronic devices. Understanding the oxidation at GaN surface is important for improving metal-oxide-semiconductor (MOS) devices. In this study, the oxidation at GaN surfaces depending on the GaN crystal planes (+c, -c, and m-plane) was investigated by real time XPS and DFT-MD simulation. We found that HO vapor has the highest reactivity due to the spin interaction between HO and GaN surfaces. The bond length between the Ga and N on the -c GaN surface was increased by OH attacking the back side of three-fold Ga atom. The chemisorption on the m-plane was dominant. The intense reactions of oxidation and Al
Ga
N formation for p-GaN were observed at the interface of the AlO
layer deposited by ALD using HO vapor. This study suggests that an oxidant gas other than HO and O should be used to avoid unintentional oxidation during AlGaN atomi layer deposition.
molecule adsorption on polar and 
-plane surfaces of GaNSumiya, Masatomo*; Sumita, Masato*; Asai, Yuya*; Tamura, Ryo*; Uedono, Akira*; Yoshigoe, Akitaka
Journal of Physical Chemistry C, 124(46), p.25282 - 25290, 2020/11
Times Cited Count：10 Percentile：40.15(Chemistry, Physical)The initial oxidation of different GaN surfaces [the polar Ga-face (+c) and N-face (-c) and the nonpolar (10
0) ()plane] under O molecular beam irradiation was studied by real-time synchrotron radiation X-ray photoelectron spectroscopy and DFT molecular dynamics calculation. The results predict that triplet O either dissociates or chemisorbs at the bridge position on the +c-surface, while on N-terminated -c-surface the O
2 molecule only undergoes dissociative chemisorption. On the -GaN surface, although the dissociation of O is dominant, the bond length and angle were found to fluctuate from those of O molecules adsorbed on the polar surfaces. The computational model including both the surface spin and polarity of GaN is useful for understanding the interface between GaN and oxide layers in metal-oxide electronic.
Sumiya, Masatomo*; Tsuda, Yasutaka; Sakamoto, Tetsuya*; Sumita, Masato*; Sang, L.*; Harada, Yoshitomo*; Yoshigoe, Akitaka
no journal, ,
no abstracts in English
Sumiya, Masatomo*; Tsuda, Yasutaka; Sumita, Masato*; Yoshigoe, Akitaka
no journal, ,
Synchrotron radiation X-ray photoelectron spectroscopy (XPS) was employed to clarify the oxidized states on the polar and m-plane GaN surfaces under exposure of various oxidation gases of HO, O, NO, and NO. It was found that HO vapor has the higher reactivity. The oxygen was hardly adsorbed on the surface by irradiating NO and NO gases. Apparently, two oxidation states for O and HO irradiation were detected on +c GaN surface. Physisorption of O molecule was dominate. The dissociation and adsorption of HO molecules co-existed on the +c surface. The chemisorption on the m-plane of GaN was dominant, and a stable Ga-O bond was formed on the surface. These chemical oxygen states were simulated by density functional molecular dynamics calculation using a theoretical model including both electronic spins on the surfaces and the polarity of GaN.
