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As a promising novel route towards highly efficient optoelectronic devices, GaN based 3D core-shell light emitting diodes (LEDs) have attracted increased attention in recent years. In comparison to conventional 2D thin film LED, the 3D LED systems using a core-shell geometry with high aspect ratio are a breakthrough in technology with lots of advantages. In this paper, we review our developed growth strategies of these LED systems on Si and sapphire substrates. A catalyst free selective area growth of GaN 3D core-shell LED systems was realized using patterned substrates by metal organic vapor phase deposition in a convenient continuous-flux growth mode. We have recently suggested that the surface polarity plays a crucial role for the morphology of GaN 3D structure growth. In order to analyze the surface polarity of 3D submicron or micron structures, Kelvin probe force microscopy and selective etching techniques have been developed. During the growth of GaN submicron rods and micron columns on patterned SiO_x/sapphire templates, mixed polarity effects could be detected. A new "truncated pyramid + column" growth method was developed to effectively avoid the formation of mixed polarity and realize single N-polar GaN 3D devices. Transmission electron microscopy and spatially and spectrally resolved cathodoluminescence measurements evidently prove the core-shell structure of 3D LED systems.

Al- and N-polar AlN have been grown by metalorganic vapor phase epitaxy (MOVPE) with the assistance of In dopant and characterized by in situ interferometry, ellipsometry, scanning electron microscopy, atomic force microscopy, and X-ray diffractometry. The growth of Al-polar AlN is faster with smoother surfaces than the N-polar ones, which is explained by theoretical calculations. The surfactant effect of In is confirmed by improving the growth rate and surface flatness without getting into the epilayer. Additionally, In is also favorable for reducing the density of dislocations and improving the crystalline quality, especially that of Al-polar AlN. The results suggest that using In surfactant to grow the Al-polar AlN epilayer leads to a better crystal quality under proper pre-growth treatments, low- and high-temperature AlN growth conditions.

In this work, we discuss the growth of dilute InAsBi nanostructures grown by metalorganic vapor phase epitaxy on GaAs substrates. The surface morphology of InAsBi nanostructures is carefully investigated, as a function of the growth temperature, by scanning electronic microscopy and atomic force microscopy. (004) High-resolution X-ray diffraction configuration has been used to characterize the crystalline quality and Bi incorporation in the InAsBi films. Low temperature and low Bi flow favor the formation of elongated nanostructures during growth. We give a quantitative description of the elemental processes for the formation of these nanostructures. Our description is based on the Tersoff and Tromp theoretical model.

Al_xGa${}_{1-x}$N films were grown on Si/N-treated sapphire substrate by atmospheric pressure metalorganic vapor phase epitaxy (AP-MOVPE) in a home-made vertical reactor. This process can be considered as randomly in situ epitaxial lateral overgrowth (ELO) technology. The growth firstly begins by three-dimensional (3D) mode and is completed in two-dimensional (2D) growth mode as shown by real time in situ laser $(\lambda =632.8$nm$)$ reflectometry measurements and confirmed by scanning electron microscopy (SEM) images. Secondary ion mass spectroscopy (SIMS) measurements evidence Al composition pulling effect in the Al_xGa${}_{1-x}$N layer. The Si/N treatment technique is compared to conventional Al_xGa${}_{1-x}$N growth techniques. The results of high-resolution X-ray diffraction (HRXRD), photoluminescence (PL) measurements and SEM images agree well on the fact that the Si/N treatment produces Al_xGa${}_{1-x}$N layers with comparable qualities of Al_xGa${}_{1-x}$N layers grown on high temperature GaN template but with much higher qualities than Al_xGa${}_{1-x}$N layers grown on low temperature AlN nucleation layer. Moreover, the Si/N treatment technique permits the growth of high quality Al_xGa${}_{1-x}$N layers with appreciable thicknesses with respect to the others techniques.

As a promising novel route towards highly efficient optoelectronic devices, GaN based 3D core-shell light emitting diodes (LEDs) have attracted increased attention in recent years. In comparison to conventional 2D thin film LED, the 3D LED systems using a core-shell geometry with high aspect ratio are a breakthrough in technology with lots of advantages. In this paper, we review our developed growth strategies of these LED systems on Si and sapphire substrates. A catalyst free selective area growth of GaN 3D core-shell LED systems was realized using patterned substrates by metal organic vapor phase deposition in a convenient continuous-flux growth mode. We have recently suggested that the surface polarity plays a crucial role for the morphology of GaN 3D structure growth. In order to analyze the surface polarity of 3D submicron or micron structures, Kelvin probe force microscopy and selective etching techniques have been developed. During the growth of GaN submicron rods and micron columns on patterned SiO_x/sapphire templates, mixed polarity effects could be detected. A new “truncated pyramid + column” growth method was developed to effectively avoid the formation of mixed polarity and realize single N-polar GaN 3D devices. Transmission electron microscopy and spatially and spectrally resolved cathodoluminescence measurements evidently prove the core-shell structure of 3D LED systems.