Strain effects on excitonic transitions in GaN: Deformation potentials

Shan, Wei; Hauenstein, R. J.; Fischer, Arthur J.; Song, J. J.; Perry, W. G.; Bremser, M. D.; Davis, R. F.; Goldenberg, B.

doi:10.1103/physrevb.54.13460

Cited by 171 publications

(102 citation statements)

References 22 publications

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“…[23][24][25] 25 The intersection of two microcracks will provide a corner in which stress relief is nearly complete, thereby providing a reference for the measurement of E X (0) in a nearly unstrained (e ii % 0) AlN region. 26,27 A CL image of two intersecting DLDs whose corner was analyzed is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…A diagonalization of the orbital-strain Hamiltonian for a wurtzite crystal permits a determination of the energy shift of the near-band edge excitonic emission as a function of the strain tensor e ij . [22][23][24] For the present case of an AlN film, we use the appropriate strain and deformation potentials for this wurtzite structure. 25 For a diagonal strain tensor e ij (i.e., where e ij 5 0 for i 6 ¼ j), the energy of the near-band edge excitonic luminescence as a function of strain E X (e) is given by E X ðeÞ 5 E X ð0Þ 1 a 1 e zz 1 a 2 e xx 1 e yy À Á 1 b 1 e zz 1 b 2 e xx 1 e yy À Á…”

Section: Resultsmentioning

confidence: 99%

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Cathodoluminescence study of micro-crack-induced stress relief for AlN films on Si(111)

Sarusi

Moshe

Khatsevich

et al. 2006

Journal of Elec Materi

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Spatially, spectrally, and depth-resolved cathodoluminescence (CL) measurements were performed for high-quality thin AlN films grown on Si(111). CL spectra exhibited a sharp peak at 5.960 eV, corresponding to the near-band-edge excitonic emission of AlN. Depth-resolved CL analysis showed that deep level oxygen and carbon impurities are localized primarily at the AlN/Si interface and AlN outer surface. Monochromatic CL imaging of the near-band-edge emission exhibits a spotty pattern, which corresponds to high concentrations of threading dislocations and thermally induced microcracks in the thin layers. We have examined relief of the thermal stress in close proximity to single microcracks and intersecting microcracks. Local CL spectra acquired with a focused e-beam show blue-shifts as large as ;82 meV in the AlN nearband edge excitonic peaks, reflecting defect-induced reductions in the biaxial thermal stress, which has a maximum value of ;47 kbar.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Cathodoluminescence study of micro-crack-induced stress relief for AlN films on Si(111)

Sarusi

Moshe

Khatsevich

et al. 2006

Journal of Elec Materi

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“…With decreasing growth temperature, a decreasing emission energy is observed corresponding to the higher indium incorporation in the QWs. 19) with a bowing parameter of 2.6 eV, which is close to the recently reported value by Moret et al 20 To take the strain induced shift of the bandgap energy into account, we used the relations given by Shan et al 21 with a linear interpolation of the elastic constants 22 and the deformation potentials. 23,24 The optical transition energies (including exciton binding energies) were then calculated for a QW thickness of 1.5 nm by numerically solving Schrö-dinger's equation assuming a band offset ratio of DE C / DE V ¼ 70:30 (Ref.…”

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confidence: 99%

Highly efficient light emission from stacking faults intersecting nonpolar GaInN quantum wells

Jönen

Rossów

Bremers

et al. 2011

Applied Physics Letters

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We report on the optical properties of m-plane GaInN/GaN quantum wells (QWs). We found that the emission energy of GaInN QWs grown on m-plane SiC is significantly lower than on nonpolar bulk GaN, which we attribute to the high density of stacking faults. Temperature and power dependent photoluminescence reveals that the GaInN QWs on SiC have almost as large internal quantum efficiencies as on bulk GaN despite the much higher defect density. Our results indicate that quantum-wire-like features formed by stacking faults intersecting the quantum wells provide a highly efficient light emission completely dominating the optical properties of the structures. V C 2011 American Institute of Physics. [doi:10.1063/1.3607301] In the past few years, GaN-based light emitting devices grown on non-polar planes have continuously attracted increasing attention due to their promising optical properties. While conventional structures grown on the polar c-plane suffer from the quantum-confined Stark effect (QCSE), 1 GaN layers grown on non-polar surfaces are free from polarization fields in growth direction. 2 The increased transition probability may result in an improved device efficiency leading to increased light output powers and/or reduced threshold current densities. 3 Indeed, the first GaInN based laser diodes with an emission wavelength at 500 nm have been shown by Okamoto et al. on m-plane GaN substrates. 4 However, up to now, non-polar GaN substrates are still barely available, small in size, and also very expensive. As an alternative, several groups have reported heteroepitaxial growth of non-polar GaN layers on foreign substrates (c-LiAlO 2 , SiC, r-plane sapphire). [5][6][7] However, most of these structures were affected by high densities of threading dislocations (TDs) and basal plane stacking faults (BSFs), which are terminated by either prismatic stacking faults (PSFs) or partial dislocations. 8 While TDs are known to act as nonradiative recombination centers, BSFs are optically active since they can be considered as cubic (zincblende) ABC phases in the wurtzite ABAB stacking sequence. Such a structure forms a type-II heterojunction which may capture electrons and holes resulting in optical transitions below the wurtzite GaN bandgap energy. 9-11 More recently, a BSF related emission from aplane GaN/AlGaN quantum well (QW) structures was reported, suggesting the formation of quantum-wire-like states in the regions where BSFs intersect the QWs. 12,13 In this paper, we investigate the optical properties of m-plane GaInN/GaN QW structures grown on silicon carbide (SiC). In particular, we show that stacking faults intersecting the QWs dominate the optical properties of these structures.Our samples were grown on m-plane 6H-SiC, m-plane bulk GaN substrates, and a-plane GaN templates (grown by hydride vapor phase epitaxy) in a low pressure metalorganic vapor phase epitaxy system with a horizontal reactor (Aixtron AIX 200RF). The precursors used were trimethylgallium, triethylgallium, trimethylaluminum, trimethylindium,...

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“…There is a discussion in the literature about whether the initial relaxation occurs over a few nm [18] or is more gradual [3]. It has been shown that thicker layers (> 3 µ m) of GaN on SiC are usually under tensile strain [4] [5], whereas thinner layers (< 0.7 µ m) are under compressive strain [3] [6]. In addition, the compressive strain introduces an increase in the bandgap and the tensile strain introduces a decrease in the bandgap of AlGaN [4] [5].…”

Section: Optical Propertiesmentioning

confidence: 99%

“…It is generally considered that the epitaxial film will relax during growth, and the major strain in the films at room temperature is related to differences in the thermal expansion. As an example, tensile strain has been reported to introduce shifts from ≈ 4 meV [4] [5] to ≈ 16 meV [6], in the case of GaN. The factors contributing to the full width at half maximum (FWHM) of the luminescence from the present AlGaN films were investigated, and it will be shown below that a significant contribution can be attributed to alloy fluctuations on a micrometer scale.…”

Section: Introductionmentioning

confidence: 99%

Compositional variation of AlGaN epitaxial films on 6H-SiC substrates determined by cathodoluminescence.

Petersson

Gustafsson

Samuelson

et al. 2002

MRS Internet j. nitride semicond. res.

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High quality epitaxial films of AlxGa1−xN, grown on SiC substrates, were investigated using spatially resolved cathodoluminescence (CL), scanning electron microscopy, and atomic force microscopy. A variation in the observed peak energy position of the CL was related to alloy fluctuations. CL was used to reveal relative alloy fluctuations of approximately 1% on a sub-micrometer scale, with a precision difficult to surpass with other available techniques. By correlating data from the different techniques, a model was derived. The main feature of it is an alloy fluctuation on the micrometer scale, seeded during the initial growth and extending through the epitaxial film. These alloy fluctuations seems to be related to terrace steps (≈5 nm in height), formed preferentially at scratches on the SiC surface. This investigation indicates that the initial growth of epitaxial films is critical and structures formed at the beginning of the growth tend to persist throughout the growth. Further, a strain gradient from the SiC interface extending towards the surface, was observed.

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Strain effects on excitonic transitions in GaN: Deformation potentials

Cited by 171 publications

References 22 publications

Cathodoluminescence study of micro-crack-induced stress relief for AlN films on Si(111)

Cathodoluminescence study of micro-crack-induced stress relief for AlN films on Si(111)

Highly efficient light emission from stacking faults intersecting nonpolar GaInN quantum wells

Compositional variation of AlGaN epitaxial films on 6H-SiC substrates determined by cathodoluminescence.

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