| Autor: |
James (Zi-Jian) Ju, Loitsch, Bernhard, Stettner, Thomas, Schuster, Fabian, Stutzmann, Martin, Koblmüller, Gregor |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 2014, Vol. 116 Issue 5, p053501-1-053501-9, 9p, 2 Color Photographs, 6 Graphs |
| Abstrakt: |
We elucidate the role of growth parameters (III/N flux ratio, temperature TG) on the morphological and structural properties, as well as compositional homogeneity and carrier localization effects of high In-content (x(In)>0.75) In-polar InGaN films grown by plasma-assisted molecular beam epitaxy (PAMBE). Variations in III/N flux ratio evidence that higher excess of In yields higher threading dislocation densities as well as larger compositional inhomogeneity as measured by x-ray diffraction. Most interestingly, by variation of growth temperature TG we find a significant tradeoff between improved morphological quality and compositional homogeneity at low-TG (~450-550 °C) versus improved threading dislocation densities at high-TG (~600-630 °C), as exemplified for InGaN films with x(In)=0.9. The enhanced compositional homogeneity mediated by low-TG growth is confirmed by systematic temperature-dependent photoluminescence (PL) spectroscopy data, such as lower PL peakwidths, >5× higher PL efficiency (less temperatureinduced quenching) and a distinctly different temperature-dependent S-shape behavior of the PL peak energy. From these, we find that the carrier localization energy is as low as ~20 meV for low-TG grown films (TG=550 °C), while it rises to ~70 meV for high-TG grown films (TG=630 °C) right below the onset of In-N dissociation. These findings point out that for the kinetically limited metal-rich PAMBE growth of high In-content InGaN a III/N flux ratio of ~1 and low-to-intermediate TG are required to realize optically more efficient materials. [ABSTRACT FROM AUTHOR] |
| Databáze: |
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