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The ZnO films were grown by low pressure metal-organic chemical vapor deposition (LP-MOCVD) using dimethylzinc (DMZn) and oxygen. The as-grown film has strong (0002) oriented characteristic, containing the chain-like network grains in small sizes, A well-resolved shoulder emission at 3.03 eV in the photoluminescence (PL) spectra has been ascribed to the interstitial zinc in the crystal, implying a serious oxygen deficiency state of the MOCVD growth, in good agreement with the analysis of XPS results. Post-annealing of the films leads to the remarkable improvement of the structure, morphology, components and optical properties. Large hexagonal columnar grains were then observed by atomic force microscope (AFM). The luminescence efficiency was enhanced greatly due to the reduction of the nonradiative defects. Meanwhile, chemisorbed oxygen gives rise to surface acceptor states, resulting in the different radiative recombination. Photoluminescence excitation measurement shows good agreement with the above conclusions. [ABSTRACT FROM AUTHOR]

Room-temperature photoluminescence spectra of Mg-implanted GaN grown on sapphire by low-pressure metal-organic chemical vapor deposition have been studied. An obvious blue emission and a broad yellow-band emission were observed. Spectra analysis suggests that, in the forbidden band of GaN, there exist four doping-related energy levels at 170 meV and 310 meV below the conduction band, and at 250 meV and 390 meV above the valence band, respectively. Transitions between these energy levels give the blue emission of 415 nm and 438 nm. Also, annealing partially recovers the GaN crystalline structure, leading to the reappearance of the yellow-band luminescence. [ABSTRACT FROM AUTHOR]

Highlights: [•] A nanoporous InGaN/GaN multiple quantum wells has been fabricated. [•] The overall external quantum efficiency for nanoporous InGaN/GaN MQWs is enhanced. [•] The nanoporous structure led to more light scattering and lower defects density. [Copyright &y& Elsevier]

Abstract: InGaN/GaN single quantum well (SQW) structures under various InGaN growth temperatures have been grown by metal organic chemical vapor deposition (MOCVD), the surface morphologies and optical properties are investigated. The radius of the typical V-pits on the SQW surface is affected by the InGaN well-temperature, and the surface roughness decreased as the well-temperature reduced. Room-temperature photoluminescence (PL) and cathode luminescence (CL) shows the quantum well and quantum dot (QD)-like localized state light emission of the SQWs grown at 700 and 690°C, respectively, whereas the samples grown at 670 and 650°C present hybrid emission peaks. Excitation power dependent PL spectra indicates the QD-like localized state emission dominates at low excitation power and the quantum well emission starts to take over at high excitation power. [Copyright &y& Elsevier]

Abstract: Selective area epitaxy has been applied to grow GaN stripe templates with side facts, followed by InGaN/GaN multiple quantum well (MQW) structures. Stripes oriented along the direction of [11−20] form smooth triangular {1−101} facets, while stripes in the [1−100] direction produce incomplete coalesced {11−22} side facets with planar (0001) surface under the same growth conditions. Room-temperature luminescence property is investigated by using photoluminescence (PL) and cathodeluminescence (CL) spectra. It is found that uniform emission at 400nm has been obtained for triangular MQWs oriented the direction of [11−20]. With respect to the MQWs grown along the [1−100] direction, large redshift is achieved for the ridge area compared to the sidewall due to the lateral vapor diffusion and surface migration. [Copyright &y& Elsevier]

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]

Photoluminescence (PL), X-ray diffraction (XRD) and Raman spectra have been measured to characterize the effects of phosphorus on the optical and structural properties of GaN1−xPx alloys with x&les;15%, grown by means of light-radiation heating, low-pressure metal-organic chemical vapor deposition. The PL spectra of GaN1−xPx show the largest red shift of 100 meV from the band-edge emission of GaN. XRD rocking curves show that the (0 0 0 2) peak of GaN1−xPx shifts to smaller angles with increasing P content. The Raman spectra of GaN1−xPx, recorded in backscattering geometry, exhibit four new vibrational modes at 256, 314, 377 and 428 cm−1 compared with an undoped GaN sample. The modes at 377 and 428 cm−1 are attributed to gap modes related to the Ga–P bond vibrations, whereas the other two modes at 256 and 314 cm−1 are assigned to phosphorus clusters and disorder-activated scattering, respectively. The frequency of the A1 (LO) mode is found to decrease with increasing x at a much high rate of approximately 268 cm−1/x for x<0.03. This red shift is attributed to the effects of alloying and strain. Furthermore, we have not observed characterizations related to GaP resulted from the phase separation from PL, XRD and Raman spectra of all investigated GaN1−xPx samples. [Copyright &y& Elsevier]

Abstract: By using chemical vapor deposition method, 4H-SiC films have been grown on AlN/Si(100) complex substrates at the temperature below 1100 °C. Substitutional Al and N are found in the SiC film. Photoluminescence (PL) peaks, related to Al acceptor and N shallow donor, respectively, have been observed at the room-temperature. The higher partial pressure ratio of SiH4 and C2H4 (P C2H4 / P SiH4 ≧1.62) results in more Si-vacancy (V Si) in the film. The PL peak related to the V Si acceptor level is also observed. [Copyright &y& Elsevier]