Investigation on the variation of the step-terrace structure on the surface of polished GaN wafer

Gong, H.; Pan, Guoshun; Zou, Chunli; Zhou, Yan; Xu, Li

doi:10.1016/j.surfin.2016.10.010

Cited by 13 publications

(6 citation statements)

References 23 publications

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“…The atomic step-terrace topography is determined by the crystal structure of GaN and shows real crystallographic information of the GaN surface. There are two distinct types of atomic step-terraces called “a–a type” and “a–b type” in different areas of the GaN surface. , The width of the “a–a type” terrace is almost the same, and the height of the “a–a type” terrace is about 0.264 nm, which is equivalent to the thickness of one Ga–N bilayer . The “a–b type” terrace features unequal widths of step a and step b, which may be ascribed to the original stacked structure of the “ABAB...” type of GaN crystal .…”

Section: Resultsmentioning

confidence: 99%

“…There are two distinct types of atomic step-terraces called “a–a type” and “a–b type” in different areas of the GaN surface. , The width of the “a–a type” terrace is almost the same, and the height of the “a–a type” terrace is about 0.264 nm, which is equivalent to the thickness of one Ga–N bilayer . The “a–b type” terrace features unequal widths of step a and step b, which may be ascribed to the original stacked structure of the “ABAB...” type of GaN crystal . The average height of the “a–b type” terrace is about 0.39 ± 0.05 nm, which probably originates from the Ga-N-Ga three-layers structure (∼0.33 nm) and is affected by the Ga 2 O 3 on the GaN surface (as XPS results show).…”

Section: Resultsmentioning

confidence: 99%

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Effective Suppression of Amorphous Ga₂O and Related Deep Levels on the GaN Surface by High-Temperature Remote Plasma Pretreatments in GaN-Based Metal–Insulator–Semiconductor Electronic Devices

Deng

Wang

Huang

et al. 2023

ACS Appl. Mater. Interfaces

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Gallium nitride (GaN) has been considered one of the most promising materials for the next-generation power and radio-frequency electronic devices, as they can operate at higher voltage, higher frequency, and higher temperature, compared with their silicon (Si) counterparts. However, the fresh GaN surface is susceptible to the natural oxidation composed of Ga 2 O 3 , Ga 2 O, and other intermediate oxidation states. Moreover, the oxidized GaN surface no longer features the distinct atomic step-terrace morphology, resulting in a degraded interface when gate or passivation dielectrics are deposited without appropriate pretreatment. It is responsible for the degraded performance of GaN-based devices such as current collapse and threshold voltage instability. In this study, the proposed high-temperature (500 °C) remote plasma pretreatments (RPPs) can play a significant role in addressing the issue of the deteriorated GaN surface exposed to air. Atomic stepterrace morphology was recovered after 500 °C-RPP due to the removal of oxides and suboxides. First-principles calculations verified that Ga 2 O at the GaN surface leads to interface states at ∼2.9 eV (E C −E ∼ 0.4 eV) in the bandgap, which is consistent with the increase of interface states at the E C −E range of 0.4−0.9 eV measured through constant-capacitance deep-level transient spectroscopy. Meanwhile, deep interface states and surface-related current collapse are well suppressed in GaN metal−insulator− semiconductor devices. These improved properties by 500 °C-RPP are generalizable to a broader range, including pre-gate and prepassivation treatment, of which a decent surface/interface is desirable for high-performance GaN-based devices.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Effective Suppression of Amorphous Ga₂O and Related Deep Levels on the GaN Surface by High-Temperature Remote Plasma Pretreatments in GaN-Based Metal–Insulator–Semiconductor Electronic Devices

Deng

Wang

Huang

et al. 2023

ACS Appl. Mater. Interfaces

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“…Figure 1f shows the atomic force microscopy (AFM) image of bare AlGaN with an atomic stepterrace topography because the c-axis orientation of the AlGaN/GaN HEMT often possesses an off-angle deflection resulting from slightly miscut c-plane sapphire substrates, not absolute 0°-off. 32 The AFM image of h-BN grown on AlGaN also shows an atomic step-terrace topography over the whole wafer (Figure 1g) (and Supporting Information, Figure S1), and the surface morphology of these samples is analogous with roughness values of 0.35−0.45 nm, indicating that the h-BN grown on AlGaN exhibits an atomically smooth surface.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Van der Waals Heterostructure of Hexagonal Boron Nitride with an AlGaN/GaN Epitaxial Wafer for High-Performance Radio Frequency Applications

Moon

Chang

Kim

et al. 2021

ACS Appl. Mater. Interfaces

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While two-dimensional (2D) hexagonal boron nitride (h-BN) is emerging as an atomically thin and dangling bond-free insulating layer for nextgeneration electronics and optoelectronics, its practical implementation into miniaturized integrated circuits has been significantly limited due to difficulties in large-scale growth directly on epitaxial semiconductor wafers. Herein, the realization of a wafer-scale h-BN van der Waals heterostructure with a 2 in. AlGaN/GaN highelectron mobility transistor (HEMT) wafer using metal−organic chemical vapor deposition is presented. The combination of state-of-the-art microscopic and spectroscopic analyses and theoretical calculations reveals that the heterointerface between ∼2.5 nm-thick h-BN and AlGaN layers is atomically sharp and exhibits a very weak van der Waals interaction without formation of a ternary or quaternary alloy that can induce undesired degradation of device performance. The fabricated AlGaN/GaN HEMT with h-BN shows very promising performance including a cutoff frequency (f T ) and maximum oscillation frequency (f MAX ) as high as 28 and 88 GHz, respectively, enabled by an effective passivation of surface defects on the HEMT wafer to deliver accurate information with minimized power loss. These findings pave the way for practical implementation of 2D materials integrated with conventional microelectronic devices and the realization of future all-2D electronics.

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“…High-efficiency, high-reliability, and long-lifespan micro/nanodevices require the nondestructive GaN substrate with subnanometer surface roughness and global geometric accuracy. Nowadays, the chemical mechanical polishing/planarization (CMP) that utilizes the coupling effect of external mechanical interactions (impact and scratch due to nanoparticles) and chemical reactions (polishing slurries) has emerged as the main processing method for hard-brittle materials to limit lattice defects and achieve global planarization effectively [7][8][9][10]. Nevertheless, the lack of fundamental understanding of mechanochemical removal mechanism at the tribological interface severely restricts the further improvement in the accuracy and efficiency of the GaN planarization during the CMP process.…”

Section: Introductionmentioning

confidence: 99%

Mechanochemical reactions of GaN-Al2O3 interface at the nanoasperity contact: Roles of crystallographic polarity and ambient humidity

et al. 2021

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Mechanochemical reactions of the GaN-Al2O3 interface offer a novel principle for scientific and technological merits in the micro-/nano-scale ultra-precision surface machining. In this work, the mechanochemical reactions on Ga- and N-faced GaN surfaces rubbed by the Al2O3 nanoasperity as a function of the environmental humidity were investigated. Experimental results indicate that the N-face exhibits much stronger mechanochemical removal over the relative humidity range of 20%–80% than the Ga-face. Increasing water molecules in environmental conditions significantly promotes the interfacial mechanochemical reactions and hence accelerates the atomic attrition on N-face. The hypothesized mechanism of the selective water-involved mechanochemical removal is associated with the dangling bond configuration, which affects the mechanically-stimulated chemical reactions via altering the activation energy barrier to form the bonding bridge across the sliding interface. These findings can enrich the understanding of the underlying mechanism of mechanochemical reactions at GaN-Al2O3 interface and a broad cognition for regulating the mechanochemical reactions widely existing in scientific and engineering applications.

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Investigation on the variation of the step-terrace structure on the surface of polished GaN wafer

Cited by 13 publications

References 23 publications

Effective Suppression of Amorphous Ga₂O and Related Deep Levels on the GaN Surface by High-Temperature Remote Plasma Pretreatments in GaN-Based Metal–Insulator–Semiconductor Electronic Devices

Effective Suppression of Amorphous Ga₂O and Related Deep Levels on the GaN Surface by High-Temperature Remote Plasma Pretreatments in GaN-Based Metal–Insulator–Semiconductor Electronic Devices

Van der Waals Heterostructure of Hexagonal Boron Nitride with an AlGaN/GaN Epitaxial Wafer for High-Performance Radio Frequency Applications

Mechanochemical reactions of GaN-Al2O3 interface at the nanoasperity contact: Roles of crystallographic polarity and ambient humidity

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Investigation on the variation of the step-terrace structure on the surface of polished GaN wafer

Cited by 13 publications

References 23 publications

Effective Suppression of Amorphous Ga2O and Related Deep Levels on the GaN Surface by High-Temperature Remote Plasma Pretreatments in GaN-Based Metal–Insulator–Semiconductor Electronic Devices

Effective Suppression of Amorphous Ga2O and Related Deep Levels on the GaN Surface by High-Temperature Remote Plasma Pretreatments in GaN-Based Metal–Insulator–Semiconductor Electronic Devices

Van der Waals Heterostructure of Hexagonal Boron Nitride with an AlGaN/GaN Epitaxial Wafer for High-Performance Radio Frequency Applications

Mechanochemical reactions of GaN-Al2O3 interface at the nanoasperity contact: Roles of crystallographic polarity and ambient humidity

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Effective Suppression of Amorphous Ga₂O and Related Deep Levels on the GaN Surface by High-Temperature Remote Plasma Pretreatments in GaN-Based Metal–Insulator–Semiconductor Electronic Devices

Effective Suppression of Amorphous Ga₂O and Related Deep Levels on the GaN Surface by High-Temperature Remote Plasma Pretreatments in GaN-Based Metal–Insulator–Semiconductor Electronic Devices