We present an exact classical solution to the problem of dipole emission in a planar multilayer light-emitting device. The inputs to the model are the photoluminescence and quantum yield of the emitter material, and the device layer thicknesses and indices of refraction. The results of the model are applied to predicting the radiant intensity of organic light-emitting diodes as a function of varying device layer thickness. It is shown that the predicted radiances are in excellent agreement with the data. We also present results for the Poynting power distribution from a randomly aligned dipole for positions both internal and external to the diodes.

An alternative method is investigated for the preparation of Si-rich SiO2 films used for the fabrication of light-emitting Si nanocrystal structures. The technique, helicon-activated reactive evaporation (HARE), combines e-beam evaporation of silicon with plasma activation of a reactive argon–oxygen atmosphere, and has the advantage of being able to produce thick, H-free films suitable for planar photonic device applications. The nanocrystal-rich films were formed by annealing as-deposited films at 1100 °C for 1 h. Room temperature photoluminescence was then measured and compared with that from ion-implanted samples annealed under similar conditions. The HARE-deposited films exhibited strong visible luminescence for a range of excess Si concentrations, demonstrating their potential for the manufacture of such materials. The films also exhibited a concentration dependence comparable to that of ion-implanted samples: the luminescence intensity initially increased with excess Si concentration up to a maximum before decreasing with increasing concentration thereafter. The cause of the decrease at higher concentrations is briefly discussed.

The observation is reported of a strong negative change in the refractive index of tin-doped thin silica films deposited by helicon activated reactive evaporation. Samples with concentrations between 5 and 25mol% SnO2 were exposed to 2 kJ/cm(2) of 248 nm UV radiation. Negative refractive index changes as large as -2.7 x 10(-3) were observed on irradiation.

Impurity-free vacancy interdiffusion of GaAs/Al/sub 0.54/Ga/sub 0.46/As quantum wells (QWs) was achieved using SiO/sub x/ capping followed by rapid thermal annealing at 950/spl deg/C. The SiO/sub x/ films were plasma deposited using N/sub 2/O/SiH/sub 4/ flow at 300/spl deg/C and 20 W rf power. The stoichiometry of capping layers were altered by varying the flowrate of N/sub 2/O. In the samples studied, the above process allows continuously variable energy shifts as high as /spl sim/15O meV while still maintaining clearly resolved excitonic behavior. The degree of intermixing is not controlled by x only but, also, by the density of the SiO/sub x/ layers, Our results, therefore, suggest that, in addition to the solid solubility of Ga in SiO/sub x/, intermixing in SiO/sub x/ capped MQW heterostructures depends on the mobility of Ga atoms in the oxide caps.

Silicon dioxide (SiO x , x ≤ 2) films were plasma-deposited at a pressure of 1 Torr and low substrate temperature (≤ 300°C) by N 2 0/lSiH 4 flow. Deposition rates in the range 20–50 nm/min were achieved at 20 W rf source power. Deep level transient spectroscopy showed that no significant defect levels were introduced in the Si substrates at this low source power. The effects of flowrate ratio, R, of N 2 O/SiH 4 and substrate temperature on film properties were determined using ex-situ spectroscopic ellipsometry, prism coupler, Rutherford backscattering spectroscopy (RBS), secondary ion mass spectrometry (SIMS), Fourier transform infrared spectroscopy (FTIR) and chemical etching (P-etch). Near-stoichiometric oxide layers were obtained for R ≥ 1, and a decrease in deposition rate with increasing R was observed. The increase in refractive index for R ≤ 1 has been correlated to compositional changes in the thin films. Complementary results were obtained from FFIR and P-etch measurements. Nitrogen was present in the films deposited using R = 4.4, for which the depostion rate showed an Arrhenius-like relationship to substrate temperature. No OH-related bands were observed in our films.

A plasma containing only silicon atoms and ions has been obtained by electron-beam evaporation of solid silicon through a helicon rf plasma source. The density of the silicon plasma in the diffusion chamber is 3–5×1010 cm−3, and the electron temperature 12 eV. These plasma conditions correspond to a predicted deposition rate from silicon ions of 230±60 nm/min, comparable to the deposition rate of 250 nm/min obtained using the same evaporation conditions, without generating a plasma. The large contribution of silicon ions, the high deposition rate, and the absence of other species such as hydrogen or argon, leads to novel conditions for plasma assisted deposition.

Existing optical fibre and fibre-device fabrication techniques have been complemented recently by the development of new processes for the fabrication of planar optical waveguides and devices. These processes rely on new forms of plasma reactors and diagnostic systems which allow in-situ control of optical parameters such as refractive index. These plasma processing systems allow the fabrication of optical devices which are not readily feasible in fibre technology, and allow the fabrication of very compact and highly complex optical circuitry which can be produced on a single photonic chip. They also offer the potential to integrate photonic devices with semiconductor sources and detectors to realise a compact, hybrid photonic-optoelectronic chip, complete with fibre pig-tailing. Because of their compactness and potential low cost, these types of photonic chips are attractive components for future high-capacity optical telecommunications and other networks now being planned as part of the information super highway. The paper presents the physical constraints and design rules for the fabrication of the devices, and the research carried out using a helicon plasma reactor to grow the thick films of silica necessary for the waveguides. From the start, the reactor was designed to process substrates at low temperatures to allow the integration with other optical and electronic components on the same wafer. Hence a considerable amount of research was carried out on the relation between the plasma parameters and the physical properties of the films deposited. The last section of the paper describes the fabrication of an actual device; a 1:8 splitter, and its characteristics.

A thin, one-dimensional, gradient-index slab lens with a parabolic profile was designed and fabricated in fluorine-doped silica by use of plasma-enhanced chemical vapor deposition in a Helicon plasma reactor. The refractive-index profile of the fabricated lens was determined by the application of an inversion technique to the values of modal effective index measured with a prism coupler. The periodic refocusing property of the lens and the independence of the wavelength were measured with the fluorescence of a specially doped, thin polymer layer spin-coated onto the surface of the lens.

The authors present the first report of an induced refractive index change in germane-silicate glass containing no detectable levels of hydrogen. The single layer waveguide was deposited on a silicon wafer by helicon activated reactive evaporation (HARE), and following exposure to 193nm UV from an excimer laser, an absolute decrease of 0.006 in refractive index was measured. The dopant level of germanium is estimated to be similar to 15% (mol).

Plasma-assisted chemical vapour deposition (PACVD) has many advantages for the deposition of thin films. The use of ions for the energetic bombardment of the film during growth is an important technique for producing dense structures. This paper discusses recent progress in the understanding of the effects of energetic bombardment on the stress levels and structure of films produced by plasma deposition processes. Diagnostic equipment, such as the in situ ellipsometer, energy selecting mass spectrometer and residual gas analyser, enables the PACVD process to be closely monitored so that conditions at the growth surface can be accurately controlled. New plasma sources, such as the helicon plasma source, give increased ion fluxes. The cathodic arc source is also an intense source of highly ionized plasma which can be used for PACVD. The deposition of rugate optical structures based on SiOxNy can be carried out using a PACVD process in which the refractive index profile is created by the computer control of gas flows. The helicon plasma source is useful for the deposition of SiO2 films and has been adapted for use in an ion plating process for the deposition of cubic phase BN. The deposition of amorphous hydrogenated carbon films by PACVD of acetylene in a cathodic arc has been shown to be possible and demonstrates the effect of using a highly ionized plasma for PACVD.

Existing optical fiber and fiber-device fabrication techniques have been complemented recently by the development of plasma enhanced chemical vapor deposition (PECVD) processes for the fabrication of buried channel waveguides and associated devices. These processes rely on new forms of plasma reactors and diagnostic systems, which allow in-situ control of optical parameters such as refractive index, and are also being complemented by the direct writing of waveguides into photosensitive PECVD materials. Both the plasma and direct-write processes allow the fabrication of optical devices which are not readily feasible in fiber technology. The low-temperature PECVD process reported here offers the potential to integrate photonic devices with semiconductor sources and detectors to realize a compact, hybrid photonic-optoelectronic chip, complete with fiber pig-tailing. Because of their compactness and potential low cost, these types of photonic chips are attractive components for future high-capacity optical telecommunications and other networks now being planned as part of the information superhighway.

An equilibrium thermodynamic analysis of the Gibbs free energy in a non-hydrostatic stress field is applied to the formation of boron nitride thin films. The theory predicts a specific sequence of microstructures from non-oriented hexagonal boron nitride, through oriented hexagonal boron nitride and finally cubic boron nitride. It also predicts a threshold stress for cubic boron nitride formation. These predictions are in agreement with experimental observations reported here and made by others. The synthesis of cubic boron nitride in a new helicon wave plasma source is demonstrated. The operating parameters which produce the cubic phase are determined.

The optical and structural properties of SiO2 films have been studied as a function of the energy of the ion bombardment applied during plasma-enhanced chemical-vapor deposition. The stress level, the degree of birefringence, and the type of microstructure on the surface and in the bulk showed systematic variations with energy. A theoretical model of the behavior of the stress developed in the layer during the deposition is compared to the experimental results. A second model developed to explain the birefringence enables the degree of columnar structure in the films to be estimated. The explanation for the variation of the refractive index with the ion energy requires the presence of a dense phase with refractive index greater than that of thermally grown SiO2. The volume fraction of the dense phase, and hence the film refractive index, is correlated with the magnitude of the compressive stress. Conditions of ion bombardment leading to optimum properties for our application were identified.