• N. A. K. Kaufmann, L. Lahourcade, B. Hourahine, D. Martin, and N. Grandjean, “Critical impact of Ehrlich-Schwöbel barrier on GaN surface morphology during homoepitaxial growth,” Journal of Crystal Growth, vol. 433, p. 36–42, 2016.
    [BibTeX] [Abstract] [Download PDF]

    We discuss the impact of kinetics, and in particular the effect of the Ehrlich-Schwöbel barrier (ESB), on the growth and surface morphology of homoepitaxial GaN layers. The presence of an ESB can lead to various self-assembled surface features, which strongly affect the surface roughness. We present an in-depth study of this phenomenon on GaN homoepitaxial layers grown by metal organic vapor phase epitaxy and molecular beam epitaxy. We show how a proper tuning of the growth parameters allows for the control of the surface morphology, independent of the growth technique.

    @Article{strathprints53732,
    author = {Nils A.K. Kaufmann and L. Lahourcade and B. Hourahine and D. Martin and N. Grandjean},
    title = {Critical impact of {E}hrlich-{S}chw{\"o}bel barrier on {GaN} surface morphology during homoepitaxial growth},
    journal = {Journal of Crystal Growth},
    year = {2016},
    volume = {433},
    pages = {36--42},
    month = {January},
    abstract = {We discuss the impact of kinetics, and in particular the effect of the Ehrlich-Schw{\"o}bel barrier (ESB), on the growth and surface morphology of homoepitaxial GaN layers. The presence of an ESB can lead to various self-assembled surface features, which strongly affect the surface roughness. We present an in-depth study of this phenomenon on GaN homoepitaxial layers grown by metal organic vapor phase epitaxy and molecular beam epitaxy. We show how a proper tuning of the growth parameters allows for the control of the surface morphology, independent of the growth technique.},
    keywords = {growth models, metalorganic chemical vapor deposition, molecular beam epitaxy, nitrides, semiconducting gallium compounds, surface structure, Physics, Electronic, Optical and Magnetic Materials, Surfaces and Interfaces},
    url = {http://strathprints.strath.ac.uk/53732/}
    }

  • A. Kaminska, P. Nowakowski, G. Staszczak, T. Suski, A. Suchocki, J. F. Carlin, N. Grandjean, R. Martin, and A. Yamamoto, “Peculiarities in the pressure dependence of photoluminescence in InAlN,” Physica Status Solidi B, vol. 250, iss. 4, p. 677–682, 2013.
    [BibTeX] [Abstract] [Download PDF]

    Studies of ambient-pressure and high-pressure behavior of photoluminescence (PL) for series of InxAl1-xN layers are presented. The measured evolution of PL energy (EPL) with x is characterized by a clear decrease of EPL and exhibits a strong bowing. This dependence corresponds to the predictions of ab initio calculations of the band-gap energy changes EG with x. However, values of EPL are clearly lower than EG, for 0{\ensuremath{<}}x{\ensuremath{<}}0.3. For higher x, the measured EPL follows well the calculated EG. The experimentally determined pressure coefficient of PL energy (dEPL/dp) shows a complicated behavior for alloys with different In-content. We found a strong reduction of dEPL/dp for 0{\ensuremath{<}}x{\ensuremath{<}}0.3 and a relatively constant magnitude of this coefficient for higher x. Moreover, for the lower x region, we observed dEPL/dp that can differ even by a factor two in samples with nominally very similar In-content. The general tendency in dEPL/dp evolution with x corresponds to lower values than calculated dEG/dp for alloys with non-uniform indium distribution. We propose two not necessary independent explanations of these experimental findings. First, due to non-uniform In distribution (induced, e.g. by defects or non-homogeneous strain) both EPL and dEPL/dp are reduced. Second, a similar behavior results from an involvement of the localized states, whose formation and contribution to PL can be induced by strain and/or native defects. In both hypotheses, the strain/defect density can significantly change around x{$\approx$}0.18 where InxAl1-xN layers are lattice matched to GaN template. {\copyright} 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    @article{strathprints48001,
    volume = {250},
    number = {4},
    month = {April},
    author = {Agata Kaminska and Piotr Nowakowski and Grzegorz Staszczak and Tadeusz Suski and Andrzej Suchocki and Jean Fran{\c c}ois Carlin and Nicolas Grandjean and Robert Martin and Akio Yamamoto},
    title = {Peculiarities in the pressure dependence of photoluminescence in InAlN},
    journal = {Physica Status Solidi B},
    pages = {677--682},
    year = {2013},
    keywords = {high-pressure spectroscopy, photoluminescence, pressure coefficients, ternary nitride alloys, InAlN, Physics, Condensed Matter Physics, Electronic, Optical and Magnetic Materials},
    url = {http://strathprints.strath.ac.uk/48001/},
    abstract = {Studies of ambient-pressure and high-pressure behavior of photoluminescence (PL) for series of InxAl1-xN layers are presented. The measured evolution of PL energy (EPL) with x is characterized by a clear decrease of EPL and exhibits a strong bowing. This dependence corresponds to the predictions of ab initio calculations of the band-gap energy changes EG with x. However, values of EPL are clearly lower than EG, for 0{\ensuremath{<}}x{\ensuremath{<}}0.3. For higher x, the measured EPL follows well the calculated EG. The experimentally determined pressure coefficient of PL energy (dEPL/dp) shows a complicated behavior for alloys with different In-content. We found a strong reduction of dEPL/dp for 0{\ensuremath{<}}x{\ensuremath{<}}0.3 and a relatively constant magnitude of this coefficient for higher x. Moreover, for the lower x region, we observed dEPL/dp that can differ even by a factor two in samples with nominally very similar In-content. The general tendency in dEPL/dp evolution with x corresponds to lower values than calculated dEG/dp for alloys with non-uniform indium distribution. We propose two not necessary independent explanations of these experimental findings. First, due to non-uniform In distribution (induced, e.g. by defects or non-homogeneous strain) both EPL and dEPL/dp are reduced. Second, a similar behavior results from an involvement of the localized states, whose formation and contribution to PL can be induced by strain and/or native defects. In both hypotheses, the strain/defect density can significantly change around x{$\approx$}0.18 where InxAl1-xN layers are lattice matched to GaN template. {\copyright} 2013 WILEY-VCH Verlag GmbH \& Co. KGaA, Weinheim.}
    }

  • K. P. O'Donnell, R. W. Martin, M. E. White, M. J. Tobin, J. F. W. Mosselmans, I. M. Watson, B. Damiliano, and N. Grandjean, "Luminescence and structural properties of InGaN epilayer, quantum well and quantum dot samples using synchrotron radiation," MRS Online Proceedings Library, vol. 639, p. G9.11, 2001.
    [BibTeX] [Abstract] [Download PDF]

    The Daresbury synchrotron radiation source (SRS) provides bright, tunable x-rays for scattering and absorption probes of local structure. Scanning confocal microscopy and luminescence decay measurements employ the SRS in alternative ways, as a tunable luminescence excitation engine and as a source of weak, 160 ps pulses with a large pulse-topulse separation, respectively. This report first describes local atomic structure studies of InGaN epilayers by extended x-ray absorption fine structure (EXAFS). In addition, we report photoluminescence (PL) imaging, PL microspectroscopy and photoluminescence decay studies of various nitride samples, including tailored InGaN quantum wells and discs.

    @article{strathprints38541,
    volume = {639},
    title = {Luminescence and structural properties of InGaN epilayer, quantum well and quantum dot samples using synchrotron radiation},
    author = {K.P. O'Donnell and R.W. Martin and M.E. White and M.J. Tobin and J.F.W. Mosselmans and I.M. Watson and B. Damiliano and N. Grandjean},
    year = {2001},
    pages = {G9.11},
    journal = {MRS Online Proceedings Library},
    keywords = {InGaN epilayer , quantum well, quantum dot samples , synchrotron radiation, Physics, Mechanics of Materials, Materials Science(all), Mechanical Engineering, Condensed Matter Physics},
    url = {http://strathprints.strath.ac.uk/38541/},
    abstract = {The Daresbury synchrotron radiation source (SRS) provides bright, tunable x-rays for scattering and absorption probes of local structure. Scanning confocal microscopy and luminescence decay measurements employ the SRS in alternative ways, as a tunable luminescence excitation engine and as a source of weak, 160 ps pulses with a large pulse-topulse separation, respectively. This report first describes local atomic structure studies of InGaN epilayers by extended x-ray absorption fine structure (EXAFS). In addition, we report photoluminescence (PL) imaging, PL microspectroscopy and photoluminescence decay studies of various nitride samples, including tailored InGaN quantum wells and discs.}
    }