Correlation between biaxial stress and free exciton transition in AlN epilayers

Pantha, B. N.; Nepal, Neeraj; Tahtamouni, T. M. Al; Nakarmi, M. L.; Li, J.; Lin, J. Y.; Jiang, Hongxing

doi:10.1063/1.2789182

Cited by 40 publications

(27 citation statements)

References 25 publications

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“…The excitonic structure of AlN, and especially the energy position of the emissions, has been demonstrated to be related to the strain state [17]. In our case, the energy positions of the excitonic emissions are comparable to strain-relaxed AlN hetero-epilayer [14,16]. This further confirms the TEM analyses reported above as well as recent Raman spectroscopy results showing that these AlN NWs are fully relaxed [18].…”

Section: Growth Of Aln Nanowiressupporting

confidence: 93%

Growth mechanism of catalyst‐free [0001] GaN and AlN nanowires on Si by molecular beam epitaxy

Landré

Fellmann

Jaffrennou

et al. 2010

Phys. Status Solidi (c)

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Real‐time in‐situ X‐rays scattering experiments were performed to study the nucleation process of GaN nanowires grown by plasma‐assisted molecular beam epitaxy on AlN(0001)/Si(111). From the comparison between the case of nanowires and the case of GaN quantum dots, it is concluded that nanowire precursor islands are completely relaxed from the beginning. Next, based on high resolution electron microscopy analysis, it is demonstrated that relaxation of nanowire precursors is associated to formation of dislocations at the AlN/GaN interface, establishing that three‐dimensional islanding and plastic strain relaxation of GaN are two necessary conditions for nanowire growth. Along the same lines, we demonstrate that three‐dimensional islanding of AlN on SiO2 leads to formation of AlN nanowires with structural and optical properties characteristic of high quality relaxed material (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Section: Growth Of Aln Nanowiressupporting

confidence: 93%

Growth mechanism of catalyst‐free [0001] GaN and AlN nanowires on Si by molecular beam epitaxy

Landré

Fellmann

Jaffrennou

et al. 2010

Phys. Status Solidi (c)

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“…Following the results from Pantha et al, the shift to higher energies is consistent with the compressive strain as observed by Raman spectroscopy. 22 Finally, the deep defect luminescence shows a one order of magnitude increase of the intensity of the emissions at 3.5 eV, 3.2 eV, and 4.4-4.7 eV for the N-polar AlN ( Figure 5(a)), which were assigned to silicon, oxygen, and Alvacancies, respectively. 23,24 This indicates that comparable to GaN or InN, increased point defect incorporation occurs on the anion side of polar AlN or increased incorporation of nonradiative defects occurs on the cation side of AlN.…”

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confidence: 99%

Polarity control and growth of lateral polarity structures in AlN

Kirste

Mita

Hussey

et al. 2013

Applied Physics Letters

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The control of the polarity of metalorganic chemical vapor deposition grown AlN on sapphire is demonstrated. Al-polar and N-polar AlN is grown side-by-side yielding a lateral polarity structure. Scanning electron microscopy measurements reveal a smooth surface for the Al-polar and a relatively rough surface for the N-polar AlN domains. Transmission electron microscopy shows mixed edge-screw type dislocations with polarity-dependent dislocation bending. Raman spectroscopy reveals compressively strained Al-polar and relaxed N-polar domains. The near band edge luminescence consists of free and bound excitons which are broadened for the Al-polar AlN. Relaxation, better optical quality, and dislocation bending in the N-polar domains are explained by the columnar growth mode.

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“…For example, the spectral peak positions of / 2 scans of both the symmetric ͑002͒ and asymmetric ͑102͒ reflection peaks of a c-plane AlN homoepilayer and AlN bulk substrate exactly line up revealing an in-plane lattice constant of a = 3.112 Å, which also indi- cate that the AlN homeepilayer is perfectly lattice matched to the AlN bulk substrate and is almost strain free. 18 The band-edge emission peak intensity ratio for a-plane, c-plane, and m-plane AlN homoepilayers is approximately 32:5:1. Due to the unique band structure of AlN near the ⌫ point, the PL intensity in a-plane AlN is enhanced by the fact that AlN exhibits a maximum emission in the directions perpendicular to the c direction ͑or in the E / /c measurement geometry͒.…”

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confidence: 99%

Photoluminescence properties of AlN homoepilayers with different orientations

Sedhain

Nepal

Nakarmi

et al. 2008

Applied Physics Letters

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AlN homoepilayers and heteroepilayers were grown on polar c-plane and nonpolar a-plane and m-plane orientations of AlN bulk and sapphire substrates by metal organic chemical vapor deposition. A systematic comparative study of photoluminescence properties of these samples revealed that all AlN homoepilayers ͑c, a and m planes͒ were strain free with an identical band gap of about 6.099 ͑6.035͒ eV at 10 ͑300͒ K, which is about 42 meV below the band gap of c-plane AlN heteroepilayers grown on sapphire. Also, nonpolar a-plane homoepilayers have the highest emission intensity over all other types of epilayers. We believe that a-plane AlN homoepilayers have the potential to provide orders of magnitude improvement in the performance of new generation deep UV photonic devices. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2965613͔ AlN has a complete solid solubility with GaN ͑Ref. 1͒ and emerged as an important semiconductor material for applications of light emitters down to 200 nm ͑Ref. 2͒ and detectors in the deep ultraviolet ͑DUV͒ and extreme UV spectral region. 3,4 Quantum wells ͑QWs͒ have been the device structure of choice for efficient III-nitride semiconductor based light emitters. 5,6 Conventional nitride c-plane multiple QW structures generate fixed sheet charges at the interfaces due to the spontaneous and piezoelectric polarization. 7-10 which induce internal electric fields, lead to carrier separation, and reduce the radiative recombination rate. Consequently, optoelectronic devices such as light emitting diodes and laser diodes based on heteroepitaxial c-plane oriented III-nitride materials possess reduced internal quantum efficiencies.There has been tremendous effort in the investigation of nonpolar a-plane and m-plane III-nitride epilayers 11 and optoelectronic devices with QW structures 9,10 to reduce the effects of internal electric fields. To achieve QW and other heterostructure based devices with improved performance, optical properties of epilayers grown on different orientations of available substrates have to be better understood. Furthermore, most previous studies on the fundamental band structures of AlN have been carried out for heteroepilayers grown on sapphires, which are plagued by lattice mismatch induced strain and high threading dislocation density, which significantly inhibited our ability for precisely determining the fundamental band structure parameters of AlN. In this work, we report a systematic comparative study of optical properties of both homoepitaxial and heteroepitaxial layers of AlN grown on polar c-plane as well as a-plane and m-plane orientations probed by DUV photoluminescence ͑PL͒.AlN bulk single crystal substrates were produced by sublimation crystal growth using polycrystalline AlN wafer as seeds and have a thickness of about 1 mm and an average grain size of about 2 ϫ 3 mm 2 . 12 The surface of AlN bulk crystal substrates was prepared by chemical mechanical polishing ͑done by NovaSiC͒ that provided a surface roughness of about 1 -4 nm. The dislocation density i...

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Correlation between biaxial stress and free exciton transition in AlN epilayers

Cited by 40 publications

References 25 publications

Growth mechanism of catalyst‐free [0001] GaN and AlN nanowires on Si by molecular beam epitaxy

Growth mechanism of catalyst‐free [0001] GaN and AlN nanowires on Si by molecular beam epitaxy

Polarity control and growth of lateral polarity structures in AlN

Photoluminescence properties of AlN homoepilayers with different orientations

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