Identification of a Cubic Phase in Epitaxial Layers of Predominantly Hexagonal GaN

Strauß, Uwe; Tews, H.; Riechert, H.; Averbeck, R.; Schienle, M.; Jobst, B.; Volm, D.; Streibl, T; Meyer, B. K.; Rühle, W. W.

doi:10.1557/s1092578300002167

Cited by 13 publications

(11 citation statements)

References 16 publications

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“…(These observations are supported by TEM measurements on similar films by Xin et al (1996) which indicate a relatively high proportion of the cubic phase close to the layer-substrate interface.) In the hexagonal phase the DBE transition occurs 32 meV below the band edge-if we assume a similar exciton binding energy in cubic material, we obtain a cubic band gap in close agreement with the 3.302 eV measured by Ramirez-Flores et al It is important, in this context, that almost all the published PL data includes reference to an emission line close to 3.27 eV, which is almost certainly excitonic in origin as indicated by the very short decay time (Klann et al 1995, Strauss et al 1997a, while Hwang et al (1994) also reported seeing both hexagonal and cubic lines from the same sample, separated by 204 meV and showing closely similar pressure coefficients. This seems strong evidence for the cubic band gap being approximately 200 meV smaller than that of hexagonal material, as we claimed earlier.…”

Section: Cubic Gansupporting

confidence: 89%

“…Straightforward analysis of this model yields a value of E A 80 meV. Somewhat similar results have been reported by Strauss et al (1996) for cubic GaN as we discuss below. In summary, we can only wait for confirmation of these speculations but the weight of evidence must favour an effective valence band mass of about 0.7 m-the evidence of exciton binding energy appears too strong to be denied.…”

Section: Electronic Propertiessupporting

confidence: 87%

“…Thus, Okamura et al (1994) described the use of both GaAs (100) and 3C SiC (β-SiC) substrates, Paisley et al (1989) and Kim et al (1994) also used β-SiC, Strite et al (1991), Hwang et al (1994), Cheng et al (1995) and Schikora et al (1996) refer to (100) GaAs, Lei et al (1991) used (100) Si substrates, Cheng et al (1995) and used (100) GaP, while Powell et al (1993) employed (100) MgO. Interestingly, Hong et al (1995) and Yang et al (1995a) have grown cubic GaN on GaAs (111) substrates (both A and B faces) and Strauss et al (1997a, b) on c-plane sapphire, even though one might expect these substrates to favour the hexagonal structure. Finally, Menniger et al (1996a) have grown mixed, micron-sized crystals of cubic and hexagonal phase GaN on (100) GaAs substrates.…”

Section: Cubic Ganmentioning

confidence: 99%

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Group III nitride semiconductors for short wavelength light-emitting devices

1998

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The group III nitrides (AlN, GaN and InN) represent an important trio of semiconductors because of their direct band gaps which span the range 1.95-6.2 eV, including the whole of the visible region and extending well out into the ultraviolet (UV) range. They form a complete series of ternary alloys which, in principle, makes available any band gap within this range and the fact that they also generate efficient luminescence has been the main driving force for their recent technological development. High brightness visible light-emitting diodes (LEDs) are now commercially available, a development which has transformed the market for LED-based full colour displays and which has opened the way to many other applications, such as in traffic lights and efficient low voltage, flat panel white light sources. Continuously operating UV laser diodes have also been demonstrated in the laboratory, exciting tremendous interest for high-density optical storage systems, UV lithography and projection displays. In a remarkably short space of time, the nitrides have therefore caught up with and, in some ways, surpassed the wide band gap II-VI compounds (ZnCdSSe) as materials for short wavelength optoelectronic devices. The purpose of this paper is to review these developments and to provide essential background material in the form of the structural, electronic and optical properties of the nitrides, relevant to these applications. We have been guided by the fact that the devices so far available are based on the binary compound GaN (which is relatively well developed at the present time), together with the ternary alloys AlGaN and InGaN, containing modest amounts of Al or In. We therefore concentrate, to a considerable extent, on the properties of GaN, then introduce those of the alloys as appropriate, emphasizing their use in the formation of the heterostructures employed in devices. The nitrides crystallize preferentially in the hexagonal wurtzite structure and devices have so far been based on this material so the majority of our paper is concerned with it, however, the cubic, zinc blende form is known for all three compounds, and cubic GaN has been the subject of sufficient work to merit a brief account in its own right. There is significant interest based on possible technological advantages, such as easier doping, easier cleaving (for laser facets) and easier contacting.

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Section: Cubic Gansupporting

confidence: 89%

Section: Electronic Propertiessupporting

confidence: 87%

Section: Cubic Ganmentioning

confidence: 99%

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Group III nitride semiconductors for short wavelength light-emitting devices

1998

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“…A multiexponential decay is observed as expected for this transition. 15 The lifetime of the DAP 1 is between 5 and 20 ns. The LO replica of the DAP band is indicated by arrows.…”

mentioning

confidence: 99%

Mechanisms of optical gain in cubic gallium nitrite

Holst

Eckey

Hoffmann

et al. 1998

Applied Physics Letters

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We report on the mechanisms of optical gain in cubic GaN. Intensity-dependent gain spectra allow a distinction of the processes involved in providing optical amplification. For moderate excitation levels, the biexciton decay is responsible for a gain structure at 3.265 eV. With increasing excitation densities, gain is observed on the high energy side of the cubic band gap due to band filling processes. For the highest pump intensities, the electron-hole plasma is the dominant gain process. Gain values up to 210 cm−1 were obtained, indicating the high potential of cubic GaN for device applications. The observed gain mechanisms are similar to those of hexagonal GaN.

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“…This line corresponds to radiative recombination of excitons bound at neutral donor (nitrogen vacancy) [9]. The two lines at 3.43 and 3.37 eV are related to oxygen impurity [10] and to a defect of unknown nature [11], respectively. An additional line related to the thick layer of In x Ga 1−x N is observed in the spectral range from 2.85 eV to 3.25 eV.…”

Section: Bulk Layers Of In X Ga 1−x N and Ganmentioning

confidence: 99%

Fabrication of Multilayer Structures and Ramp-Edge Josephson Junctions with (Hg,Re)Ba₂CaCu₂O_y Films

Ogawa¹,

Sugano²,

Wakana³

et al. 2006

jjap

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We have grown bulk In x Ga 1−x N films and In x Ga 1−x N/GaN (x 0.1) multiple quantum well structures on Al 2 O 3 substrates by electron cyclotron resonance assisted molecular beam epitaxy. We have not found any signs of phase separation in bulk films with low indium content, x 0.1. However, we observed inhomogeneous spatial distribution of indium with x varying from 0.1 to 0.2. In multiple quantum well structures with thin In x Ga 1−x N layers non-homogeneity was absent under certain growth conditions. Exposure of In x Ga 1−x N/GaN multiple quantum well structures to pulses of a nitrogen laser with power density I 10 6 W cm −2 led to irreversible changes in both luminescence and reflection spectra. These results, as well as chemical analysis of irradiated surface layers performed using Auger electron spectroscopy, indicate that intensive laser irradiation decreases nitrogen content in the crystal lattice of GaN and gives rise to surface metallization.

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Identification of a Cubic Phase in Epitaxial Layers of Predominantly Hexagonal GaN

Cited by 13 publications

References 16 publications

Group III nitride semiconductors for short wavelength light-emitting devices

Group III nitride semiconductors for short wavelength light-emitting devices

Mechanisms of optical gain in cubic gallium nitrite

Fabrication of Multilayer Structures and Ramp-Edge Josephson Junctions with (Hg,Re)Ba₂CaCu₂O_y Films

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Identification of a Cubic Phase in Epitaxial Layers of Predominantly Hexagonal GaN

Cited by 13 publications

References 16 publications

Group III nitride semiconductors for short wavelength light-emitting devices

Group III nitride semiconductors for short wavelength light-emitting devices

Mechanisms of optical gain in cubic gallium nitrite

Fabrication of Multilayer Structures and Ramp-Edge Josephson Junctions with (Hg,Re)Ba2CaCu2Oy Films

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Product

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Fabrication of Multilayer Structures and Ramp-Edge Josephson Junctions with (Hg,Re)Ba₂CaCu₂O_y Films