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We investigated the suitability of aluminum nitride (AlN) for surface passivation and protection of gallium arsenide (GaAs), using a low-temperature passivation method. By varying the plasma power (100, 200 W) during etching, we found that 200 W produced better passivation. Using X-ray photoelectron spectroscopy, we quantitatively demonstrate that etching the GaAs at 200 W almost removed the GaAs oxide layer. To further study the surface passivation of GaAs, we deposited an AlN film by plasma-enhanced atomic layer deposition using trimethylaluminum and ammonia precursors at 250 °C. AlN passivation did not effectively smooth the GaAs surface, but did increase its photoluminescence intensity. This study shows that AlN coating by plasma-enhanced atomic layer deposition is a promising low-temperature method for GaAs surface passivation. [ABSTRACT FROM AUTHOR]

In this work, we perform a sulfur chemical passivation on GaAs substrate, which leads to a change in the photoluminescence (PL) owing to a reduction of surface states. By varying the reaction time of passivation, we can modify the chemical bonds of the GaAs surface and reduce the surface depletion region thickness, which strongly affects the emission efficiency of the GaAs band edge. Based on systematic PL measurements and energy band model with surface states, the sulfur passivation also enhances the number of free and bound excitons. Therefore, sulfur passivation is important to improve the performance of GaAs-based optoelectronics devices. [ABSTRACT FROM AUTHOR]

Surface passivation is an effective way to eliminate the surface states and to improve the optical properties of GaAs. Moreover, carriers restriction of wide bandgap materials also is a path to enhance photoluminescence. In this paper, Be-doped GaAs epilayer was growth on GaAs substrate by molecular beam epitaxy. The MgO films were deposited by atom layer deposition. It was used as not only passivation layer to eliminate surface states, but also barrier layer to restrict carriers. The carriers restriction was confirmed by photoluminescence and current-voltage characteristics of metal-insulator-semiconductor structure. As the result, the photoluminescence intensity of Be-doped GaAs with 5 nm MgO was 2.5 times higher than the bare Be-doped GaAs. [ABSTRACT FROM AUTHOR]

Aiming to modification the surface optical properties, CdS/ZnO composites were synthesized by hydrothermal method. The ZnO/CdS heterostructures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (EDS), photoluminescence (PL) measurements at room temperature and the temperature-dependent photoluminescence treatment. In the room temperature PL spectra, the defect-related deep level emission can effectively suppress under optimal CdS deposition condition. With the increasing of CdS deposition time to 150 min, the donor bound exciton (D0X) peak showed a significantly red shift at low temperature (77K) PL spectrum. Through analysis the temperature-dependent photoluminescence spectra, we find that it was caused by acceptor bound exciton (A0X). Meanwhile, there appeared a donor-acceptor pair related emission at lower-energy side of the spectrum. The experiment demonstrated that the surface donor defects can effectively suppresse after CdS nanoparticles deposition on ZnO nanorods. [ABSTRACT FROM PUBLISHER]

As a kind of semiconductor material, the morphology of zinc oxide directly affects its physical properties. By adjusting the ratio of the reaction source and the rate of the incoming gas flow, we obtained one-dimensional nanowire and two-dimensional nanoflag-like functional gradient material (FGM) using chemical vapor deposition (CVD) method. Compared with the one-dimensional nanowires, the growth of the two-dimensional ZnO FGM not only c-oriented, but other directions are also appeared. Photoluminescence results show that the FGM has a higher visible/UV emission intensity ratio than the nanowires for several orders of magnitudes. Meanwhile, the growth mechanism of these nanostructures were discussed in details. [ABSTRACT FROM AUTHOR]

Phosphorus doped ZnO nanoparticles have been synthesized by simple thermal decomposition. By adjusting the concentration of reaction sources, different doping concentrations nanoparticals were obtained and kept wurtzite structure. The EDX and XPS results confirmed P incorporated in ZnO lattice and formed PZn-2VZn complex acceptor. In low temperature PL spectra and temperature dependent PL spectra, the emission peak located at 3.350 eV, 3.310 eV and 3.241 eV could be observed which were attributed to A0X, FA and DAP. Then, the increasing of P-doping concentrations would cause the energy of acceptor bound exciton became lower, and enhance the intensity of FA emission. [ABSTRACT FROM AUTHOR]

Etching and sulfuring are equally important process during the surface sulfur passivation of gallium antimopnide (GaSb) In this work, we described the effects of etching by certain proportion of bromine methanol solution instead of hydrochloric acid solution (acidification), which could lead to a improvement of surface passivation homogeneity of GaSb. The photoluminescence (PL) spectra and the atomic force microscope (AFM) morphology on GaSb are also indicated a good surface morphology. [ABSTRACT FROM AUTHOR]