High reactivity of H ₂ O vapor on GaN surfaces

Abstract

Understanding the process of oxidation on the surface of GaN is important for improving metal-oxide-semiconductor (MOS) devices. Real-time X-ray photoelectron spectroscopy was used to observe the dynamic adsorption behavior of GaN surfaces upon irradiation of H 2 O, O 2 , N 2 O, and NO gases. It was found that H 2 O vapor has the highest reactivity on the surface despite its lower oxidation power. The adsorption behavior of H 2 O was explained by the density functional molecular dynamic calculation including the spin state of the surfaces. Two types of adsorbed H 2 O molecules were present on the (0001) ( +c ) surface: non-dissociatively adsorbed H 2 O (physisorption), and dissociatively adsorbed H 2 O (chemisorption) molecules that were dissociated with OH and H adsorbed on Ga atoms. H 2 O molecules attacked the back side of three-fold Ga atoms on the (0001̅) (− c ) GaN surface, and the bond length between the Ga and N was broken. The chemisorption on the (101̅0) m -plane of GaN, which is the channel of a trench-type GaN MOS power transistor, was dominant, and a stable Ga-O bond was formed due to the elongated bond length of Ga on the surface. In the atomic layer deposition process of the Al 2 O 3 layer using H 2 O vapor, the reactions caused at the interface were more remarkable for p -GaN. If unintentional oxidation can be resulted in the generation of the defects at the MOS interface, these results suggest that oxidant gases other than H 2 O and O 2 should be used to avoid uncontrollable oxidation on GaN surfaces.

Wet‐Etching‐Boosted Charge Storage in 1D Nitride‐Based Systems for Imitating Biological Synaptic Behaviors

“…According to the electronic structure results in previous researches, H 2 O and O 2 molecules can adsorb onto the surface without spin flipping because H 2 O and O 2 can choose the spin state of the electrons donated to the surface. [41,42] The lone pairs of oxygen in the H 2 O and O 2 molecules approach the Ga atom on the GaN surface, and the OH − and O 2− can contribute an electron with a spin opposite to the dangling bond on the GaN surface. [41,42] When the switch was placed in a vacuum ambient, the device had no memristive characteristics or conductivity.…”

“…[41,42] The lone pairs of oxygen in the H 2 O and O 2 molecules approach the Ga atom on the GaN surface, and the OH − and O 2− can contribute an electron with a spin opposite to the dangling bond on the GaN surface. [41,42] When the switch was placed in a vacuum ambient, the device had no memristive characteristics or conductivity. When the relative humidity was 68%, numerous OH − and O 2− ions were produced around the GaN NWs; these ions assisted in the formation of conductive paths on the NW surface and contributed to enhanced conductivity and memristive characteristics.…”

QCforever: A Quantum Chemistry Wrapper for Everyone to Use in Black-Box Optimization

“…Quantum chemical (QC) , computation is also one of them. In contrast to the expectation, QC computation has been mainly used as a tool to clarify chemical phenomena through QC software packages. − Although QC computation is still developing, many chemical phenomena for which no experimental information is available have been explained by QC computation. − To make black-box optimization efficient by incorporating QC computation instead of chemical experiments, we should develop an automated QC system whose input is a molecule and output is its properties.…”

“…14 − 16 Although QC computation is still developing, 17 many chemical phenomena for which no experimental information is available have been explained by QC computation. 18 − 23 To make black-box optimization efficient by incorporating QC computation instead of chemical experiments, we should develop an automated QC system whose input is a molecule and output is its properties.…”

Enhanced field-effect mobility (>250 cm2/V·s) in GaN MOSFETs with deposited gate oxides via mist CVD

“…17) Additionally, the GaO x thickness on GaN epitaxial layers varies by the oxidation conditions such as oxidant gases, oxidation time, and temperature. [18][19][20][21] Previous reports have discussed the channel mobility of GaN MOSFETs with SiO 2 film deposition using plasma-enhanced CVD (PE-CVD), 10,22) remote PE-CVD, 12,23) atomic layer deposition (ALD), 24) and low pressure CVD (LPCVD). 25) However, reports on enhancing the mobility through oxidation control are still limited.…”