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The 3G30-Advanced, AZUR SPACE's latest qualified solar cell product, provides highest end-of-life efficiencies in space. The cell reaches 27.8% at a fluence of 5 E14 cm -2 and 26.5% at a fluence of 1 E15 cm -2 1 MeV electrons. The cell mass can be reduced to a minimum by substrate thinning, the cell cost can be reduced by implementation of large area configurations and even higher radiation hardness can be achieved by using AZUR's proprietary 3G30-1E16+ design. Various configurations are currently in production. The increasing demand for cells suited for LEO applications, made AZUR to develop a novel upright metamorphic triple junction solar cell with a BOL efficiency of 31% designed for a fluence of 1 E14 cm -2 1 MeV electrons. This cell design is already in production. AZUR's next generation product 4G32 comprises an upright metamorphic 4-junction device with 28.5% EOL (1 E15 cm -2 1 MeV electrons) efficiency. Hence, the 4G32 even surpasses the EOL efficiency of the lattice-matched 3-junction cell 3G30-Advanced. It utilizes the excess current of the Ge subcell by a metamorphic cell concept and a fourth junction added to the stack. This cell will be qualified by mid-2017. This paper summarizes the results and achievements for various 3G and 4G solar cell products from AZUR SPACE, including radiation hardness and cell formats.

Abstract-In this work the advantages of GaN HEMTs grown on native GaN substrates over GaN/Si or GaN/Sapphire substrates are investigated, and correlated with epitaxial quality. TEM plane view and cross section analysis of GaN/GaN revealed dislocation density lower than 1 × 10 6 cm −2 , which is at least 3 orders of magnitude lower than the case of GaN/Si or GaN/Sapphire. In the case of GaN/Si, the dislocations did not necessarily originate from the substrate/nucleation layer interface, but the strain relief and isolation buffer stacks were main contributors to the dislocation density. GaN/GaN HEMTs demonstrated superior electrical and thermal performance. GaN/GaN demonstrated 3 orders of magnitude lower off-state leakage, current collapse (Ron increase) after stress bias less than 15% compared to 50% in the case of GaN/Si, and 2% drop of the onstate current due to self-heating in DC operation as compared to 13% and 16% for GaN/Si and GaN/Sapphire respectively. The GaN/Si thermal performance approached GaN/GaN only by substrate removal. Therefore GaN/GaN can allow high on-state current, low off-state leakage current, minimal current collapse, and enhanced thermal dissipation capability at the same time, which can be directly correlated to the absence of high dislocation densities.

67 11130Semipolar InGaN/GaN single quantum wells (SQWs) grown on {1122} planes of an inverted pyramid surface and {1011} facets of single self assembled pyramids have been studied by spatially, spectrally, and time-resolved cathodoluminescence (CL) microscopy. Mappings of local spectra and local transients provide the distribution of spectral and time-resolved luminescence properties by peak wavelength images, time delayed CL images (TDCLIs), and initial lifetime maps. The SQW on inverse pyramids exhibit strong local differences in recombination kinetics -two orders of magnitude change in initial lifetime -correlated with a giant shift in emission energy of $1 eV along a facet. For single pyramids a migration process of indium adatoms from the upper facet to the edges leads to an emission of longer wavelengths at the edges and shorter wavelengths at the upper facet with respect to the base.

Pyramidal GaN structures were deposited by selective metalorganic vapor phase epitaxy (MOVPE) to create semipolar facets. On top of these pyramids InGaN was deposited forming nanostructures of different dimensionality according to the varying strain regions along the pyramid. We have studied the emission properties of pyramid ensembles using low-temperature time-resolved photoluminescence (PL) spectroscopy. The observed PL spectra in conjunction with the revealed decay times indicate already the expectations of regions with different confinement on the pyramids. Changing the size of the pyramids and the indium supply lead to variations in the emission wavelength of the ensemble. Spatially resolved cathodoluminescence (CL) experiments were performed to analyze locally the emission properties all over the pyramidal structures. We have found that indeed the indium accumulates at the edges and the apex of the pyramids. Furthermore the emission of the quantum well (QW) sidewalls exhibit also a shift in emission energy which can be attributed again to a change of the In-content or a change of the QW thickness.