GaN-based LED wafers with nano-folding InGaN/GaN multiple quantum wells (MQWs) are grown on n-GaN nanopillar array templates which are fabricated using self assembled Ni nanodots as etching mask. Photoluminescence (PL) spectra of the wafer show uniform light emission wavelength over the whole area of it. No blue shift of the main peak is observed in the electroluminescence (EL) spectra of the LED devices fabricated with the wafer as the injection current increases from 10 mA to 80 mA. This can be ascribed to the reduced quantum confinement Stark effect (QCSE) and the resulting less band gap tilted by strain relaxation in the nano-folded MQWs. The device shows an excellent rectifying behavior with a forward voltage of 4.6 V under 20 mA injection current.

The effects of fast neutron irradiation on oxygen atoms in Czochralski silicon (CZ-Si) are investigated systemically by using Fourier transform infrared (FTIR) spectrometer and positron annihilation technique (PAT). Through isochronal annealing, it is found that the trend of variation in interstitial oxygen concentration ([Oi]) in fast neutrons irradiated CZ-Si fluctuates largely with temperature increasing, especially between 500 and 700°C. After the CZ-Si is annealed at 600°C, the V4 appearing as three-dimensional vacancy clusters causes the formation of the molecule-like oxygen clusters, and more importantly these dimers with small binding energies (0.1–1.0eV) can diffuse into the Si lattices more easily than single oxygen atoms, thereby leading to the strong oxygen agglomerations. When the CZ-Si is annealed at temperature increasing up to 700°C, three-dimensional vacancy clusters disappear and the oxygen agglomerations decompose into single oxygen atoms (O) at interstitial sites. Results from FTIR spectrometer and PAT provide an insight into the nature of the [Oi] at temperatures between 500 and 700°C. It turns out that the large fluctuation of [Oi] after short-time annealing from 500 to 700°C results from the transformation of fast neutron irradiation defects.