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A metal layer formed on the backside of InGaN/sapphire-based light-emitting diodes deteriorates the inherent optical power output. An experimental approach of a suspended die is employed to study the effects of such metal layers via a direct comparison in radiant flux from a discrete die with and without a reflector. A sphere package that employs no reflector is proposed and fabricated. Light extraction of the sphere design is discussed; a light source in the sphere package would not have to be either an ideal point or placed at the center of the sphere, due to a finite critical angle at the sphere/air interface. OCIS codes: 230.3670, 160.6000.

Discusses a study which compared the electrical properties for near-noble transition-metal-based ohmic contacts with a M/Zn/M sandwiched structure prepared on p-type indium phosphide (InP). Experimental procedures of the study; Contact resistance measurements; Microstructural analysis using x-ray diffraction and cross-sectional transmission electron microscopy (XTEM); Interdiffusion of nickel and lead with InP.

Quantization effects on optical polarization switching in (1122)-oriented InGaN/GaN quantum-well (QW) structures, which were not evident in the previous report by Ueda et al., have been firmly confirmed. The present study found that polarization ratios became more negative as the luminescence photon energy was decreased from 2.6 eV. Enhancement in optical polarization was found in thin QW structures, which is believed to be a result of quantization effects. Sample structures containing thick InGaN and AlGaN layers showed polarization ratios shifted towards positive values; these samples exhibited in-plane luminescence inhomogeneity with stripe morphologies parallel to [1100] and dark lines appearing at angles between 50 and 62° with respect to [1100]. [ABSTRACT FROM AUTHOR]

Continuous-wave (CW) operations of semipolar (1 12 2) plane InGaN/GaN laser diodes (LDs) were demonstrated. The LD structures were grown on low extended defect density semipolar (1 12 2) GaN bulk substrates, using conventional metal organic chemical vapor deposition (MOCVD) at atmospheric pressure. The threshold current was 54 mA (6.5 kA/cm2) for the CW operation [39 mA (4.6 kA/cm2) for pulsed mode]. Stimulated emission was observed at 405.9 nm with a spectral line-width of 1 nm. These results indicate that semipolar (1 12 2) GaN is a promising orientation for the realization of blue-green and green LDs. [ABSTRACT FROM AUTHOR]

Semipolar (1122) plane III–nitride laser diodes (LDs) were realized on low extended defect density semipolar (1122) GaN bulk substrates. The LD structures were grown by conventional atmospheric-pressure metal organic chemical vapor deposition (MOCVD), using conditions similar to that of c-plane nitride device growth. The mirror facet for a laser cavity was formed by dry-etching of III–V nitride films without cleaving. Stimulated emission was observed at 426.9 nm with a full width at half maximum (FWHM) of less than 1 nm. The (1122) plane laser diode had threshold currents (Ith) of 306 mA, corresponding to a threshold current densities (Jth) of 12.8 kA/cm2. [ABSTRACT FROM AUTHOR]

Electroluminescence (EL) efficiency of the InGaN-based light-emitting diode (LED) is the present subject of discussion. An equivalent circuit model was introduced to treat explicitly four independent current components: leakage, radiative, nonradiative, and carrier overflow. This model was used to explain the internal quantum efficiency (IQE) as a function of current, temperature, and material quality. In the low-current range, efficiency became strongly dependent on temperature as leakage and nonradiative recombination currents related to material quality shared a large part of the total current. In the high-current range, the reduced efficiency was explained by electron-overflow current. Electron-overflow current was increased by reducing temperature via freeze-out of holes. When leakage current and carrier overflow were suppressed effectively in the intermediate current range on high-quality devices, hole freeze-out was observed experimentally in electroluminescence intensity as temperature was varied. [ABSTRACT FROM AUTHOR]

We grew epitaxial layers on 4 H -silicon carbide (SiC) Si-face substrates with a 1° off-angle. The suppression of 3 C -inclusion formation during growth at a high C/Si ratio was investigated, because a growth technique with a high C/Si ratio is needed to decrease residual nitrogen incorporation. 3 C inclusions were generated both at the interface between the substrate and epitaxial layer, and during epitaxial growth. 3 C -SiC nucleation is proposed to trigger the formation of 3 C inclusions. We suppressed 3 C -inclusion formation by performing deep in situ etching and using a high C/Si ratio, which removed substrate surface damage and improved the 4 H -SiC stability, respectively. The as-grown epitaxial layers had rough surfaces because of step bunching due to the deep in situ etching, but the rough surface became smooth after chemical mechanical polishing treatment. These techniques allow the growth of epitaxial layers with 1° off-angles for a wide range of doping concentrations.