Structural and optical properties of pseudomorphic InxGa1−xN alloys

Romano, L. T.; Krusor, B. S.; McCluskey, M. D.; Bour, D. P.; Nauka, K.

doi:10.1063/1.122272

Cited by 63 publications

(42 citation statements)

References 11 publications

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“…11,12 For pseudomorphic In x Ga 1Ϫx N films grown on GaN͑0001͒, the termination of the dislocation gives rise to a specific type of pit known alternatively as an inverted hexagonal pyramid ͑IHP͒, a hexagonal pinhole, or as a V defect. [6][7][8][9][10] In forming an IHP, a hexagonal region of the ͑0001͒ surface is replaced with six (101 គ 1) sidewall facets, as indicated schematically in Fig. 1.…”

Section: Fritz-haber-institut Der Max-planck-gesellschaft Faradaywegmentioning

confidence: 99%

“…2 Investigations have revealed many interesting features of epitaxial In x Ga 1Ϫx N films including compositional fluctuations, 3 chemical ordering, 4 surfactant behavior, 5 and the formation of a unique defect, the inverted hexagonal pyramid defect. [6][7][8][9][10] To understand and eventually gain control over these phenomena, which directly affect the optoelectronic properties of the material, it is essential to know how In interacts with the surface of the growing film. In this article we present theoretical studies to determine the behavior of In on GaN surfaces.…”

Section: Fritz-haber-institut Der Max-planck-gesellschaft Faradaywegmentioning

confidence: 99%

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Indium-induced changes in GaN(0001) surface morphology

1999

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Section: Fritz-haber-institut Der Max-planck-gesellschaft Faradaywegmentioning

confidence: 99%

Section: Fritz-haber-institut Der Max-planck-gesellschaft Faradaywegmentioning

confidence: 99%

Indium-induced changes in GaN(0001) surface morphology

1999

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“…This value was obtained by taking into account that the InGaN layers are pseudomorphically strained as discussed recently. 7 The period of the superlattice peaks ͑12.4 nm͒ in the XRD spectrum corresponds very well to the total well and barrier thickness as determined from TEM.…”

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confidence: 99%

Structural and optical properties of epitaxially overgrown third-order gratings for InGaN/GaN-based distributed feedback lasers

Romano

Hofstetter

McCluskey

et al. 1998

Applied Physics Letters

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Laser-diode heterostructures of InGaAlN containing a third-order diffraction grating for distributed optical feedback have been examined with transmission electron microscopy ͑TEM͒ and scanning electron microscopy ͑SEM͒. The grating was defined holographically and etched by chemically assisted ion-beam etching into the upper GaN confinement layer of the laser structure. After the etch step, it was overgrown with an Al 0.08 Ga 0.92 N upper cladding layer. Threading dislocations were present that initiated at the sapphire substrate, but no new dislocations were observed at the grating/Al 0.08 Ga 0.92 N interface. A comparison of TEM and SEM micrographs reveals that there is a compositional gradient in the AlGaN upper cladding layer; however, calculations show that it did not reduce the optical coupling coefficient of the grating.Within the last couple of years, research on semiconductor lasers with emission wavelengths around 400 nm has received a great deal of attention. Recent milestones in the development of nitride-based light emitters have been the demonstration of high-brightness blue/green light emitting diodes and both pulsed and continuous-wave laser operation at room temperature. [1][2][3][4][5] Mainly for the purpose of overcoming difficulties in high-quality mirror fabrication, but also in order to improve mode selection and wavelength stability, distributed feedback ͑DFB͒ blue lasers have been demonstrated recently.6 Etching and regrowth of the grating, which typically completes the device structure, is a major obstacle for the fabrication of DFB lasers in material systems other than the nitrides. The strong chemical bonds between gallium and nitrogen result in a very stable and chemically inert surface, compared to GaAs materials for example, where oxides are readily formed on the surface.In this letter, we present a structural evaluation of a third-order diffraction grating from InGaN/GaN-based DFB lasers. The grating was defined by holography and etched into the GaN upper confinement layer by chemically assisted ion-beam etching ͑CAIBE͒. After etching, it was overgrown with an Al 0.08 Ga 0.92 N upper cladding layer and a GaN contact layer. We compare scanning electron microscopy ͑SEM͒ and transmission electron microscopy ͑TEM͒ cross sections of the grating before and after overgrowth. Based on these observations, we estimate how an effective alteration of the grating profile due to a compositional gradient might affect the grating's coupling coefficient and thus the threshold gain of the laser.The fabrication of these devices relied on growing a 4 m thick n-type GaN:Si layer on C-face sapphire. On top of this layer, we grew a 500 nm thick, n-type Al 0.08 Ga 0.92 N:Si lower cladding layer, a 100 nm thick n-type GaN:Si lower waveguiding layer, an active region with five 3.5 nm thick In 0.1 Ga 0.9 N quantum wells and 9.0 nm thick GaN barriers, and a 180 nm thick p-type GaN:Mg upper waveguiding layer. More details about growth conditions and doping levels can be found in Ref. 5. The thicknesses of the ...

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“…Nevertheless, it is often assumed that for thin layers, say below 100 nm, In x Ga 1Ϫx N grows pseudomorphically (c InGaN ϭc GaN ) to the GaN buffer. 7,13,22 In this case measuring only c InGaN and solving Eq. ͑1͒, x can be calculated.…”

mentioning

confidence: 99%

“…A deviation from a linear dependence of the fundamental gap has been postulated, with a wide range of bowing parameters, in the literature. [6][7][8][9][10][11][12][13][14] Several sources of error hamper the establishment of a consensual relation. In some studies the measured quantity is the luminescence peak energy, with ignores the Stokes' shifted 15,16 of emission with respect to the band edge.…”

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confidence: 99%

Compositional dependence of the strain-free optical band gap in InxGa1−xN layers

Pereira

Correia

Monteiro

et al. 2001

Applied Physics Letters

113

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The effect of strain on the compositional and optical properties of a set of epitaxial single layers of In x Ga 1Ϫx N was studied. Indium content was measured free from the effects of strain by Rutherford backscattering spectrometry. Accurate knowledge of the In mole fraction, combined with x-ray diffraction measurements, allows perpendicular strain (⑀ zz ) to be evaluated. Optical band gaps were determined by absorption spectroscopy and corrected for strain. Following this approach, the strain free dependence of the optical band gap in In x Ga 1Ϫx N alloys was determined for xр0.25. Our results indicate an ''anomalous,'' linear, dependence of the energy gap on the In content, at room temperature: E g (x)ϭ3.39-3.57x eV. Extension of this behavior to higher concentrations is discussed on the basis of reported results.

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Structural and optical properties of pseudomorphic InxGa1−xN alloys

Cited by 63 publications

References 11 publications

Indium-induced changes in GaN(0001) surface morphology

Indium-induced changes in GaN(0001) surface morphology

Structural and optical properties of epitaxially overgrown third-order gratings for InGaN/GaN-based distributed feedback lasers

Compositional dependence of the strain-free optical band gap in InxGa1−xN layers

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