Precise determination of surface band bending in Ga-polar n-GaN films by angular dependent X-Ray photoemission spectroscopy

Zhao, Yanfei; Gao, Hongwei; Huang, Rong; Huang, Zhiwen; Li, Fangsen; Feng, Jiagui; Sun, Qian; Dingsun, An; Yang, Hui

doi:10.1038/s41598-019-53236-9

Cited by 21 publications

(14 citation statements)

References 23 publications

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“…for n-GaN and downward −1.6 eV for p-GaN. [41][42][43] If our hypothesis is correct, the effect of the implantation-induced surface charges seems to override these natural band-bendings. We also checked for a possible influence of the fluence rate of implantations by varying the 27 Mg beam current over an order of magnitude, but no such effect was found.…”

Section: Resultsmentioning

confidence: 73%

“…Note that without artificial surface charges there is an upward band-bending around +1.5 eV for n-GaN and downward −1.6 eV for p-GaN. [41][42][43] b) In p-type GaN:Mg [Figure 2 (2.5×10 6 events), i.e. more than three times faster.…”

Section: Resultsmentioning

confidence: 99%

“…Note that without artificial surface charges there is an upward band‐bending around +1.5 eV for n ‐GaN and downward −1.6 eV for p ‐GaN. [ 41–43 ]…”

Section: Resultsmentioning

confidence: 99%

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Lattice Location Studies of the Amphoteric Nature of Implanted Mg in GaN

Wahl

Correia

Costa

et al. 2021

Adv Elect Materials

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Despite the renewed interest in ion implantation doping of GaN, efficient electrical activation remains a challenge. The lattice location of 27Mg is investigated in GaN of different doping types as a function of implantation temperature and fluence at CERN's ISOLDE facility. The amphoteric nature of Mg is elucidated, i.e., the concurrent occupation of substitutional Ga and interstitial sites: following room temperature ultra‐low fluence (≈2 × 1010 cm−2) implantation, the interstitial fraction of Mg is highest (20–24%) in GaN pre‐doped with stable Mg during growth, and lowest (2–6%) in n‐GaN:Si, while undoped GaN shows an intermediate interstitial fraction of 10–12%. Both for p‐ and n‐GaN prolonged implantations cause interstitial 27Mg to approach the levels found for undoped GaN. Implanting above 400 °C progressively converts interstitial Mg to substitutional Ga sites due to the onset of Mg interstitial migration (estimated activation energy 1.5–2.3 eV) and combination with Ga vacancies. In all sample types, implantations above a fluence of 1014 cm−2 result in >95% substitutional Mg. Ion implantation is hence a very efficient method to introduce Mg into substitutional Ga sites, i.e., challenges toward high electrical activation of implanted Mg are not related to lack of substitutional incorporation.

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Section: Resultsmentioning

confidence: 73%

Section: Resultsmentioning

confidence: 99%

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Lattice Location Studies of the Amphoteric Nature of Implanted Mg in GaN

Wahl

Correia

Costa

et al. 2021

Adv Elect Materials

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“…Given that the probing depth of XPS for GaN is about 5-6 nm (ref. 33 ), such a difference in signal-to-noise ratio (Fig. 3c-f and Supplementary Fig.…”

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confidence: 92%

Development of a photoelectrochemically self-improving Si/GaN photocathode for efficient and durable H2 production

et al. 2021

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Development of an efficient yet durable photoelectrode is of paramount importance for deployment of solar-fuel production. Here, we report the photoelectrochemically self-improving behaviour of a silicon/gallium nitride photocathode active for hydrogen production with a Faradaic efficiency approaching ~100%. By using a correlative approach based on different spectroscopic and microscopic techniques, as well as density functional theory calculations, we provide a mechanistic understanding of the chemical transformation that is the origin of the self-improving behaviour. A thin layer of gallium oxynitride forms on the side walls of the gallium nitride grains, via a partial oxygen substitution at nitrogen sites, and displays a higher density of catalytic sites for the hydrogen-evolving reaction. This work demonstrates that the chemical transformation of gallium nitride into gallium oxynitride leads to sustained operation and enhanced catalytic activity, thus showing promise for oxynitride layers as protective catalytic coatings for hydrogen evolution.

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“…Based on the apparent binding energy and line shape in ADXPS measurements, surface band bending and internal potential gradient can be calculated. 33 The principle and calculation method have been speci ed previously. [33][34][35][36] Brie y, a measured apparent core level spectrum is actually an integration of photoelectrons emitting from a depth of d 0 , and can be given by Declarations Figures Figure 1 (a) Ball model of Td-WTe2 with surface oxidation.…”

Section: Methodsmentioning

confidence: 99%

Surface band bending in semimetal Td-WTe2

Chen

Huang

et al. 2020

Preprint

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Recently, spontaneous out-of-plane electric polarization and ferroelectric switching were found in WTe2 devices. On single crystal with ferroelectric property, a built-in electric field and corresponding band bending would be expected at the surface. However, such band bending in WTe2 hasn’t directly been observed experimentally. Here, by fitting angle-dependent X-ray photoelectron spectroscopy (XPS) spectra on WTe2 surface, we clearly observed downward band bending after slightly exposure to air, verifying appearance of surface polarization. Such band bending can’t be observed on pristine WTe2 surface and will disappear on fully oxidized sample. It suggests strong correlation between surface band bending and oxidation. Ionized donors from oxide species pinned at surface may contribute to the formation of surface band bending and polarization. Our study here offers new insight to figure out the microscopic origin of ferroelectric in WTe2.

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Precise determination of surface band bending in Ga-polar n-GaN films by angular dependent X-Ray photoemission spectroscopy

Cited by 21 publications

References 23 publications

Lattice Location Studies of the Amphoteric Nature of Implanted Mg in GaN

Lattice Location Studies of the Amphoteric Nature of Implanted Mg in GaN

Development of a photoelectrochemically self-improving Si/GaN photocathode for efficient and durable H2 production

Surface band bending in semimetal Td-WTe2

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