Polarity determination for GaN thin films by electron energy-loss spectroscopy

Kong, Xiang-Shan; Hu, Guan-Qin; Duan, Xiaofeng; Lü, Yuan; Liu, X. L.

doi:10.1063/1.1504876

Cited by 17 publications

(8 citation statements)

References 17 publications

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“…4, and claim 3 is related to the dependence of impurity adsorption on the polar surface, as discussed in Sec. 5 In order to extend the possibilities of techniques based on the TEM, efforts have been made continuously to observe atomic alignment with high-resolution image matching [24], to introduce micro-channeling effects during EDS analysis [25], to detect the N K-edge and Ga L-edge during EELS analysis [26], or to count dif-fracted electrons quantitatively [27]. The polarity can also be evaluated by these new approaches.…”

Section: : Cbedmentioning

confidence: 99%

Review of polarity determination and control of GaN

Sumiya

Fuke

2004

MRS Internet j. nitride semicond. res.

121

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Polarity issues affecting III-V nitride semiconductors are reviewed with respect to their determination and control. A set of conditions crucial to the polarity control of GaN is provided for each of the following growth techniques; molecular beam epitaxy (MBE), pulsed laser deposition (PLD) and hydride vapor phase epitaxy (HVPE). Although GaN films might have been deposited by identical growth methods using the same buffer layer technologies, there is often a conflict between the resulting polarities achieved by different research groups. In this paper, we present the implications of the conditions used in each of the processes used for two-step metalorganic chemical vapor deposition (MOCVD), demonstrating systematic control of the polarity of GaN films on sapphire substrates. The potential for confusion in polarity control will be explained, taking into account the implications clarified in our studies. The correlation between the polarity and the growth conditions will be discussed in order to provide a mechanism for the determination and control of the crystal polarity during the growth of GaN films.

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Section: : Cbedmentioning

confidence: 99%

Review of polarity determination and control of GaN

Sumiya

Fuke

2004

MRS Internet j. nitride semicond. res.

121

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“…EELS signals exhibit a remarkable difference between (0002) and (0002̅) Bragg conditions that can be used to identify NW polarity. , Figure a displays the EELS spectra of the GaN NWs grown on Al-polar AlN taken at (0002) and (0002̅) Bragg conditions after subtracting the background of the N K-edge and normalizing to the Ga L-edges. Based on the fact that the N K-edge peak at the (0002) orientation should show a higher intensity, the comparison with the TEM images (cf.…”

mentioning

confidence: 99%

Spontaneous Nucleation and Growth of GaN Nanowires: The Fundamental Role of Crystal Polarity

et al. 2012

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We experimentally investigate whether crystal polarity affects the growth of GaN nanowires in plasma-assisted molecular beam epitaxy and whether their formation has to be induced by defects. For this purpose, we prepare smooth and coherently strained AlN layers on 6H-SiC(0001) and SiC(0001̅) substrates to ensure a well-defined polarity and an absence of structural and morphological defects. On N-polar AlN, a homogeneous and dense N-polar GaN nanowire array forms, evidencing that GaN nanowires form spontaneously in the absence of defects. On Al-polar AlN, we do not observe the formation of Ga-polar GaN NWs. Instead, sparse N-polar GaN nanowires grow embedded in a Ga-polar GaN layer. These N-polar GaN nanowires are shown to be accidental in that the necessary polarity inversion is induced by the formation of Si(x)N. The present findings thus demonstrate that spontaneously formed GaN nanowires are irrevocably N-polar. Due to the strong impact of the polarity on the properties of GaN-based devices, these results are not only essential to understand the spontaneous formation of GaN nanowires but also of high technological relevance.

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“…From weak beam dark field image TEM data on sample S1, the screw-and edge-dislocation densities are estimated in (1.0×10 8 ) cm −2 and (8.1×10 9 ) cm −2 , respectively, while for sample S4, are of the order of (6.62×10 8 ) cm −2 and (1.26×10 10 ) cm −2 . In the calculation, the average specimen thickness is established by counting the dark fringes in the BF image under two beam conditions, and the extinction distance of GaN used in the calculation is ξ 0 = 56 nm [41].…”

Section: Resultsmentioning

confidence: 99%

Controlling a three dimensional electron slab of graded AlxGa1−xN

Adhikari

Capuzzo

et al. 2016

Applied Physics Letters

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Polarization induced degenerate n-type doping with electron concentrations up to ∼10 20 cm −3 is achieved in graded Al x Ga 1−x N layers (x: 0%→37%) grown on unintentionally doped and on n-doped GaN:Si buffer/reservoir layers by metal organic vapor phase epitaxy. High resolution x-ray diffraction, transmission electron microscopy and electron energy loss spectroscopy confirm the gradient in the composition of the Al x Ga 1−x N layers, while magnetotransport studies reveal the formation of a three dimensional electron slab, whose conductivity can be adjusted through the GaN(:Si) buffer/reservoir. * rajdeep.adhikari@jku.at † alberta.

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Polarity determination for GaN thin films by electron energy-loss spectroscopy

Cited by 17 publications

References 17 publications

Review of polarity determination and control of GaN

Review of polarity determination and control of GaN

Spontaneous Nucleation and Growth of GaN Nanowires: The Fundamental Role of Crystal Polarity

Controlling a three dimensional electron slab of graded AlxGa1−xN

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