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Abstract: Quaternary AlInGaN quantum wells in GaN barriers were grown by metal-organic vapor-phase epitaxy. Changing to a growth sequence with pulsed metal-organic supply leads to structures with enhanced photoluminescence efficiencies. The amount of material was varied, resulting in AlInGaN layer thicknesses between nominally 1.5 and 10nm. We have analyzed the material properties by X-ray diffraction (XRD) as well as photoluminescence (PL) spectroscopy. The observed XRD-spectra and the PL intensity show the high quality of the deposited material. By analyzing the PL spectra, we have found an energy shift of the resonance lines from 2.65 to 3.33eV with decreasing well thickness. We attribute this shift mainly to the presence of internal electric fields in the AlInGaN/GaN heterostructures. Power-dependent and time-resolved PL experiments confirm this observation. By properly adjusting the material composition, we could achieve polarization field compensation of the quaternary QW structures. Also, first luminescence experiments on ternary InGaN QW embedded in quaternary barrier material were performed. [Copyright &y& Elsevier]

Abstract: The growth of GaInN quantum dots, emitting in the green spectral range, by selective epitaxy is presented in this paper. With this approach we are able to control the position of the dot completely during the growth, which is essential for functionalising of a single quantum dot. For this purpose we have studied the selective growth of hexagonal pyramids on a GaN buffer layer, masked with , by MOVPE. After the proper build-up of the pyramid, these templates were overgrown by InGaN to form a quantum dot on top of the pyramids. To investigate the optical emission of the fabricated nanostructures, the samples were capped by GaN and photoluminescence, and also time-resolved measurements were performed. [Copyright &y& Elsevier]

Abstract: We report the growth and characterisation of AlInGaN by metalorganic vapor phase epitaxy (MOVPE). The thick layers (approx. 50nm) have been grown with various TMAl flows, carrier gases and growth temperature to investigate their influence on the structural and optical properties. Our main interest is the reduction of the built-in electric field related to the strain in the layer. For that reason, high-resolution X-ray diffraction (XRD), Rutherford backscatter spectrometry (RBS) and photoluminescence (PL) enable us to determine the strain state, lattice constant and luminescence energy, depending on the quaternary composition. Quantum wells were also grown in model device structures in order to determine their utility in optoelectronic applications. [Copyright &y& Elsevier]

Abstract: AlInGaN offers many possibilities for optoelectronic applications in the blue and ultraviolet emission range. Since band gap and lattice constant can be adjusted independently, the following reduction of strain and defects in the active layer will enhance some characteristics of nitride laser diodes, like output power or lifetime. For quantum dot structures, ultra-low threshold, high material gain and improved temperature stability have been theoretically predicted. We investigate the growth of AlInGaN and the formation mechanism of quantum dots depending on the main epitaxy parameters like growth temperature, amount of deposited material, TMAl flow or even its carrier gas. At 760C, a narrow distribution of quantum dots was achieved, and depending on the growth conditions, the maximum dot density was about dots/cm and with average heights of 30nm. Photoluminescence measurements of uncapped samples showed narrow emission peaks between 2.7 and 2.95eV. [Copyright &y& Elsevier]