Quantitative study of nitridated sapphire surfaces by x-ray photoelectron spectroscopy

Hashimoto, Tadao; Terakoshi, Yoshitami; Yuri, Masaaki; Ishida, M.; Imafuji, Osamu; Sugino, Takashi; Itoh, Kunio

doi:10.1063/1.371276

Cited by 17 publications

(12 citation statements)

References 30 publications

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“…Ex situ measurements have been extensively used to study the nitridation process under different chemical processing conditions. 2,3,7,[10][11][12]15,18,23 …”

Section: Resultsmentioning

confidence: 99%

“…The normalized concentration of N 1s and O 1s was calculated from the XPS peak area divided by the corresponding atomic sensitivity factor ͑ASF͒ and normalized with the Al 2p peak area. The Al 2p peak was commonly used as a reference in sapphire nitridation studies 4,[11][12][13][14][15][16][17][18][19] since the vapor pressure of aluminum containing species ͑e.g., AlO, Al 2 O, and Al͒ is negligible at 1100°C. 24 The concentration of surface aluminum atoms was assumed therefore to be approximately constant before and after nitridation.…”

Section: Methodsmentioning

confidence: 99%

“…30,31 The Al 2p peak is commonly used as reference for other elemental peaks in previous nitridation studies. 4,[11][12][13][14][15][16][17][18][19] The Al 2p peak serves as a reference since the vapor pressure of aluminum containing species, e.g., AlO, Al 2 O, and Al, is negligible at 1100°C. Thus, the concentration or total amount of surface aluminum atoms were considered constant before and after nitridation.…”

Section: B Angle-resolved Xpsmentioning

confidence: 99%

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X-ray photoelectron spectroscopic study on sapphire nitridation for GaN growth by hydride vapor phase epitaxy: Nitridation mechanism

Dwikusuma

Kuech

2003

Journal of Applied Physics

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The nitridation of c-plane sapphire within the hydride vapor phase epitaxy system was systematically studied as a function of time and ammonia partial pressure using ex situ x-ray photoelectron spectroscopy, reflection high-energy electron diffraction, and atomic force microscopy. During the nitridation process, nitrogen was incorporated into the sapphire surface. There were two different nitrogen chemical bonding states, which can be attributed to N-Al bonds and nitrogen in oxygen-rich environment ͑'N-O'͒. As the nitridation continued, the N 1s intensity increased while the O 1s intensity decreased indicating the growth of a nitrogen-rich layer. The sapphire nitridation process can be modeled as a diffusion couple of AlN and Al 2 O 3 , where N 3Ϫ and O 2Ϫ interdiffuse in the rigid Al 3ϩ framework. Nitrogen diffuses into sapphire and substitutes for oxygen to bond with aluminum. The bond substitution is accompanied by structural changes where the AlN in-plane direction is rotated 30°with respect to the sapphire direction. The replaced oxygen diffuses out to the surface, combines with hydrogen and desorbs as H 2 O. The overall nitridation rate is determined by the slower of the two moving anions. From the x-ray photoelectron spectroscopy data, the chemical diffusion coefficient of nitrogen (D N ) and oxygen (D O ), were estimated. D N was found to be higher than D O , which suggested that the overall nitridation rate was controlled by the diffusion of oxygen to the surface. After nitridation, no protrusions were observed on the surface and no significant changes in the surface roughness were measured when compared to the as-received sapphire.

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“…Ex situ measurements have been extensively used to study the nitridation process under different chemical processing conditions. 2,3,7,[10][11][12]15,18,23 …”

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: B Angle-resolved Xpsmentioning

confidence: 99%

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X-ray photoelectron spectroscopic study on sapphire nitridation for GaN growth by hydride vapor phase epitaxy: Nitridation mechanism

Dwikusuma

Kuech

2003

Journal of Applied Physics

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“…It has been found that a thin layer of AlN is formed during this step [78,79]. In fact, the growth of an AlN [80] or a low temperature GaN [81][82][83] buffer layer has been intentionally introduced at the initial stage to improve crystal quality.…”

Section: The Aspect Of Gan Epitaxy Substrate Selectionmentioning

confidence: 99%

CVD solutions for new directions in SiC and GaN epitaxy

Li¹

2015

Linköping Studies in Science and Technology. Dissertations

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This thesis aims to develop a chemical vapor deposition (CVD) process for the new directions in both silicon carbon (SiC) and gallium nitride (GaN) epitaxial growth. The properties of the grown epitaxial layers are investigated in detail in order to have a deep understanding. SiC is a promising wide band gap semiconductor material which could be utilized for fabricating high-power and high-frequency devices. 3C-SiC is the only polytype with a cubic structure and has superior physical properties over other common SiC polytypes, such as high hole/electron mobility and low interface trap density with oxide. Due to lack of commercial native substrates, 3C-SiC is mainly grown on the cheap silicon (Si) substrates. However, there’s a large mismatch in both lattice constants and thermal expansion coefficients leading to a high density of defects in the epitaxial layers. In paper 1, the new CVD solution for growing high quality double-position-boundaries free 3C-SiC using on-axis 4H-SiC substrates is presented. Reproducible growth parameters, including temperature, C/Si ratio, ramp-up condition, Si/H2 ratio, N2 addition and pressure, are covered in this study. GaN is another attractive wide band gap semiconductor for power devices and optoelectronic applications. In the GaN-based transistors, carbon is often exploited to dope the buffer layer to be semi-insulating in order to isolate the device active region from the substrate. The conventional way is to use the carbon atoms on the gallium precursor and control the incorporation by tuning the process parameters, e.g. temperature, pressure. However, there’s a risk of obtaining bad morphology and thickness uniformity if the CVD process is not operated in an optimal condition. In addition, carbon source from the graphite insulation and improper coated graphite susceptor may also contribute to the doping in a CVD reactor, which is very difficult to be controlled in a reproducible way. Therefore, in paper 2, intentional carbon doping of (0001) GaN using six hydrocarbon precursors, i.e. methane (CH4), ethylene (C2H4), acetylene (C2H2), propane (C3H8), iso-butane (i-C4H10) and trimethylamine (N(CH3)3), have been explored. In paper 3, propane is chosen for carbon doping when growing the high electron mobility transistor (HEMT) structure on a quarter of 3-inch 4H-SiC wafer. The quality of epitaxial layer and fabricated devices is evaluated. In paper 4, the behaviour of carbon doping using carbon atoms from the gallium precursor, trimethylgallium (Ga(CH3)3), is explained by thermochemical and quantum chemical modelling and compared with the experimental results. GaN is commonly grown on foreign substrates, such as sapphire (Al2O3), Si and SiC, resulting in high stress and high threading dislocation densities. Hence, bulk GaN substrates are preferred for epitaxy. In paper 5, the morphological, structural and luminescence properties of GaN epitaxial layers grown on N-face free-standing GaN substrates are studied since the N-face GaN has advantageous characteristics compared to the Ga...

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“…A step at the interface is observed in this figure though the atomic interfacial structure cannot be clearly observed most lightly because of sapphire surface rugosity. These stepped interfaces may be a result of the large nitridation time on the sapphire [32,33].…”

Section: Epitaxial Relationship Between the A-plane Gan And R-plane Smentioning

confidence: 99%

Defects in a-GaN grown on r-sapphire by hydride vapor phase epitaxy

Dasilva

Zhu

Martin

et al. 2011

Journal of Crystal Growth

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Quantitative study of nitridated sapphire surfaces by x-ray photoelectron spectroscopy

Cited by 17 publications

References 30 publications

X-ray photoelectron spectroscopic study on sapphire nitridation for GaN growth by hydride vapor phase epitaxy: Nitridation mechanism

X-ray photoelectron spectroscopic study on sapphire nitridation for GaN growth by hydride vapor phase epitaxy: Nitridation mechanism

CVD solutions for new directions in SiC and GaN epitaxy

Defects in a-GaN grown on r-sapphire by hydride vapor phase epitaxy

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