Electron microscopy studies of the intermediate layers at the SiO₂/GaN interface

Abstract

As the first step toward understanding the electrical properties of SiO2/GaN systems, the interface was characterized using high-resolution scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS). An epitaxial crystalline intermediate layer with a thickness of ∼1.5 nm was observed at the SiO2/GaN interface. STEM-EDS analyses revealed that this intermediate layer contained gallium and oxygen and mostly comprised the ε-Ga2O3 phase. The ε-Ga2O3/GaN interface was atomically smooth and free from misfit dislocations despite lattice mismatch of ∼8.0%, suggesting that the initial oxidation of GaN surfaces is crucial to achieve good interfacial properties.

Effects of surface treatment on Fermi level pinning at metal/GaN interfaces formed on homoepitaxial GaN layers

“…However, even this kind of oxide layer can consist of multiple crystalline forms with disordered phases and Ga-related defects 28,30) . Therefore, an uncontrolled surface oxide layer may be a source of disorder at the GaN surface and metal/GaN interfaces, although a "well-controlled" native oxide layer has been reported to reduce the interface state density at the insulator/GaN interface [31][32][33] . According to the disorder-induced gap state (DIGS) model 8) , the origin of Fermi level pinning at the surface and interfaces is the gap states induced by disorder in chemical bonding.…”

The Influence of Ga–OH Bond at Initial GaN Surface on the Electrical Characteristics of SiO2/GaN Interface

“…The formation of a Ga oxide layer at the SiO 2 /GaN interface layer has also been observed . After depositing the SiO 2 layer by PECVD with tetraethyl orthosilicate (TEOS) gas and O 2 plasma, a 1.5 nm‐thick Ga 2 O 3 phase formed at the SiO 2 /GaN interface . However, the SiO 2 /GaN interface remains insufficiently understood.…”

Dynamic Observation and Theoretical Analysis of Initial O2 Molecule Adsorption on Polar and m-Plane Surfaces of GaN

“…Conventionally, an oxide layer of Al 2 O 3 or SiO 2 is deposited on the GaN layer. The surface of the GaN layer is either unintentionally oxidized during this process or intentionally oxidized via thermal oxidation or plasma treatment . There is still controversy as to whether the GaO x layer formed at the interface between the oxide and GaN layers effectively reduces the interface defect. − …”

“…In addition to this fundamental scientific interest, precise control of the reaction at the atomic scale is required for constructing efficient MOS structures in electronic devices. Thus, the mechanism of O 2 adsorption is attracting considerable attention, and many experimental and theoretical studies have been reported. − However, a number of issues remain concerning the mechanism of the dissociative adsorption of O 2 . The most widely used experimental methods for investigating surface reaction dynamics are the reactive molecule beam scattering technique and X-ray photoelectron spectroscopy (XPS).…”