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Abstract: The effect of alloying and expitaxial mismatch strain on the surface ultraviolet (UV) emission efficiencies of AlxGa1−xN films, pseudomorphically grown on both c- and m-plane AlyGa1−yN templates (x−0.03+1.79x−0.06x2 (0

Abstract: In this paper, hydrogenated amorphous silicon nitride (a-SiN x :H) films have been deposited using an electron cyclotron resonance chemical vapor deposition system. The effect of NH3 flow rate R on the deposition rate, structure and luminescence were studied using various techniques such as optical emission spectroscopy, Fourier Transform Infrared absorption (FTIR), X-ray photoelectron spectroscopy (XPS) and fluoro-spectroscopy, respectively. Optical emission behavior of SiH4 +NH3 plasma shows that atomic Si radical concentration determines the film deposition rate. Structural transition of a-SiN x film from Si-rich one to near-stoichiometric/N-rich one with R was revealed by FTIR and the two phase separation of a-Si and a-Si3N4 was also convinced in Si-rich SiN x films by XPS. Either photo- or electroluminescence for all the SiN x films with R >3 sccm shows a strong light emission in visible light wavelength range. As R <6 sccm, recombination of electrons and holes in a-Si quantum dots is the main mechanism of photo/electroluminescence for Si-rich SiN x films, however, for photoluminescence, gap states'' luminescence is also in competition; as R >6 sccm, light emission of the SiN x film originates from defect states in its band gap. [Copyright &y& Elsevier]

Abstract: The high-temperature characteristics of strain in Al0.22Ga0.78N layers, with and without a Si3N4 passivation layer, were investigated at temperatures from room temperature to 813 K by means of high-resolution X-ray diffraction. The results show that a small temperature-dependent strain relaxation occurs in the unpassivated Al0.22Ga0.78N layers when the temperature exceeds 523 K. After passivating, an additional tensile strain and an initial increase of the in-plane tensile strain with increasing temperature were observed in Al0.22Ga0.78N layers, and at higher temperatures the in-plane tensile strain only decreases slightly in the 100-nm-thick Al0.22Ga0.78N layer, but a pronounced temperature-dependent strain relaxation occurs in the 50-nm-thick one due to the fact that the thickness of the Al0.22Ga0.78N layer is close to the critical thickness, and hence the increase of tensile strain induced by passivation will result in partial strain relaxation via the formation of cracks or the glide motion and multiplication of dislocations. [Copyright &y& Elsevier]