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Abstract: The annealing behavior of 400keV Er ions implanted in silicon-on-insulator samples is investigated by Rutherford backscattering spectrometry. It is found that the SiO2/Si(Er)/SiO2 heterostructure is formed after annealing in O2 and N2 atmospheres successively at 1000°C. Only a small portion of the Er atoms segregated to the surface of the SOI sample. For the SOI sample co-implanted with Er and O ions, there is no evident out-diffusion of Er atoms to the SOI surface after annealing in a N2 atmosphere at 1000°C and highly Er and SiO x doped Si is realized. [Copyright &y& Elsevier]

Photoluminescence (PL) spectra of two different green InGaN/GaN multiple quantum well (MQW) samples S1 and S2, respectively with a higher growth temperature and a lower growth temperature of InGaN well layers are analyzed over a wide temperature range of 6 K–330 K and an excitation power range of 0.001 mW–75 mW. The excitation power-dependent PL peak energy and linewidth at 6 K show that in an initial excitation power range, the emission process of the MQW is dominated simultaneously by the combined effects of the carrier scattering and Coulomb screening for both the samples, and both the carrier scattering effect and the Coulomb screening effect are stronger for S2 than those for S1; in the highest excitation power range, the emission process of the MQWs is dominated by the filling effect of the high-energy localized states for S1, and by the Coulomb screening effect for S2. The behaviors can be attributed to the fact that sample S2 should have a higher amount of In content in the InGaN well layers than S1 because of the lower growth temperature, and this results in a stronger component fluctuation-induced potential fluctuation and a stronger well/barrier lattice mismatch-induced quantum-confined Stark effect. This explanation is also supported by other relevant measurements of the samples, such as temperature-dependent peak energy and excitation-power-dependent internal quantum efficiency. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) properties of blue multiple InGaN/GaN quantum well (BMQW) and green multiple InGaN/GaN quantum well (GMQW) formed on a single sapphire substrate are investigated. The results indicate that the peak energy of GMQW-related emission (PG) exhibits more significant "S-shaped" dependence on temperature than that of BMQW-related emission (PB), and the excitation power-dependent carrier-scattering effect is observed only in the PG emission; the excitation power-dependent total blue-shift (narrowing) of peak position (line-width) for the PG emission is more significant than that for the PB emission; the GMQW shows a lower internal quantum efficiency than the BMQW. All of these results can be attributed to the fact that the GMQW has higher indium content than the BMQW due to its lower growth temperature and late growth, and the higher indium content in the GMQW induces a more significant compositional fluctuation, a stronger quantum confined Stark effect, and more non-radiative centers. [ABSTRACT FROM AUTHOR]

The annealing behaviour of 400 keV Er ions at a fluence of 2×1015 cm-2 implanted into silicon-on-insulator (SOI) samples is investigated by Rutherford backscattering spectrometry of 2.1 MeV He2+ ions with a multiple scattering model. It is found that the damage close to the SOI surface is almost removed after being annealed in O2 and N2 atmospheres, successively, at 900 °C, and that only a small number of the Er atoms segregated to the surface of the SOI sample, whereas a large number of Er atoms diffused to a deeper position because of the affinity of Er for oxygen. For the SOI sample co-implanted with Er and O ions, there is no evident outdiffusion of Er atoms to the SOI surface after being annealed in N2 atmosphere at 900 °C. [ABSTRACT FROM AUTHOR]

ZnO thin film growth prefers different orientations on the etched and unetched SrTiO3(STO)(110) substrates. Inclined ZnO and cobalt-doped ZnO (ZnCoO) thin films are grown on unetched STO(110) substrates using oxygen plasma assisted molecular beam epitaxy, with the c-axis 42° inclined from the normal STO(110) surface. The growth geometries are ZnCoO[100]//STO[11¯0] and ZnCoO[11¯1]//STO[001]. The low temperature photoluminescence spectra of the inclined ZnO and ZnCoO films are dominated by D0X emissions associated with A0X emissions, and the characteristic emissions for the 2E(2G)→4A2(4F) transition of Co2+ dopants and the relevant phonon-participated emissions are observed in the ZnCoO film, indicating the incorporation of Co2+ ions at the lattice positions of the Zn2+ ions. The c-axis inclined ZnCoO film shows ferromagnetic properties at room temperature. [ABSTRACT FROM AUTHOR]

Quasi-aligned GaN layer-built nanotowers on silicon (111) substrates by employing ultrathin Ni catalyst films have been grown at 800 °C in a metal-organic chemical vapor deposition system. The nanotower size and the degree of alignment were found to be highly sensitive to changes in the Ni catalyst film thickness. The several growth stages of nanotowers were examined by microscopic technique, which indicates the variation in surface morphology from Ni islands to hexagonal prismatic GaN particles, and finally to GaN layer-built nanotowers. For the third stage, the growth may be attributed to an asymmetric and step by step copying process. [ABSTRACT FROM AUTHOR]

Excitation power and temperature-dependent photoluminescence (PL) spectra of the ZnTe epilayer grown on (100) GaAs substrate and ZnTe bulk crystal are investigated. The measurement results show that both the structures are of good structural quality due to their sharp bound excitonic emissions and absence of the deep level structural defect-related emissions. Furthermore, in contrast to the ZnTe bulk crystal, although excitonic emissions for the ZnTe epilayer are somewhat weak, perhaps due to As atoms diffusing from the GaAs substrate into the ZnTe epilayer and/or because of the strain-induced degradation of the crystalline quality of the ZnTe epilayer, neither the donor–acceptor pair (DAP) nor conduction band-acceptor (e–A) emissions are observed in the ZnTe epilayer. This indicates that by further optimizing the growth process it is possible to obtain a high-crystalline quality ZnTe heteroepitaxial layer that is comparable to the ZnTe bulk crystal. [ABSTRACT FROM AUTHOR]

In this study rectangular AlGaN/AlN/GaN heterostructure field-effect transistors (HFETs) with 22-nm and 12-nm AlGaN barrier layers are fabricated, respectively. Using the measured capacitance–voltage and current–voltage characteristics of the prepared devices with different Schottky areas, it is found that after processing the device, the polarization Coulomb field (PCF) scattering is induced and has an important influence on the two-dimensional electron gas electron mobility. Moreover, the influence of PCF scattering on the electron mobility is enhanced by reducing the AlGaN barrier thickness. This leads to the quite different variation of the electron mobility with gate bias when compared with the AlGaN barrier thickness. This mainly happens because the thinner AlGaN barrier layer suffers from a much stronger electrical field when applying a gate bias, which gives rise to a stronger converse piezoelectric effect. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) properties of a green and blue light-emitting InGaN/GaN multiple quantum well structure with a strong phase separated into quasi-quantum dots (QDs) and an InGaN matrix in the InGaN epilayer are investigated. The excitation power dependences of QD-related green emissions (PD) and matrix-related blue emissions (PM) in the low excitation power range of the PL peak energy and line-width indicate that at 6 K both PM and PD are dominated by the combined action of Coulomb screening and localized state filling effect. However, at 300 K, PM is dominated by the non-radiative recombination of the carriers in the InGaN matrix, while PD is influenced by the carriers transferred from the shallower QDs to deeper QDs by tunnelling. This is consistent with the excitation power dependence of the PL efficiency for the emission. [ABSTRACT FROM AUTHOR]