We report on the growth of the high-quality GaN grain on a r-plane sapphire substrate by using a self-organized SiN interlayer as a selective growth mask.Transmission electron microscopy,scanning electron microscopy,and Raman spectroscopy are used to reveal the effect of SiN on the overgrown a-plane GaN growth.The SiN layer effectively terminates the propagation of the threading dislocation and basal plane stacking faults during a-plane GaN regrowth through the interlayer,resulting in the window region shrinking from a rectangle to a "black hole".Furthermore,strong yellow luminescence(YL) in the nonpolar plane and very weak YL in the semipolar plane on the GaN grain is revealed by cathodoluminescence,suggesting that C-involved defects are responsible for the YL. 相似文献
Semipolar (11\bar 2 \bar 2) ZnO was successfully grown on (112) LaAlO3/(LaAlO3)0.29(Sr2AlTaO6)0.35 substrate by pulsed laser deposition. The epitaxial relationship is [11\bar 23]_{\rm ZnO} // [11\bar 1]_{\rm LAO/LSAT} with the polar axis of [000\bar 1]_{\rm ZnO} pointing to the surface. For ZnO films with thickness of 1.6 μm, the threading dislocation density is ~1 × 109 cm–2, and the density of basal stacking faults is below 1 × 104 cm–1. The (11\bar 2 \bar 2) ZnO exhibits strong D0X emissions with a FWHM of 9 meV and very few green–yellow emissions in the low‐temperature (10 K) and room‐temperature photoluminescence spectra, respectively.
Solid‐state lighting (SSL) is now the most efficient source of high color quality white light ever created. Nevertheless, the blue InGaN light‐emitting diodes (LEDs) that are the light engine of SSL still have significant performance limitations. Foremost among these is the decrease in efficiency at high input current densities widely known as “efficiency droop.” Efficiency droop limits input power densities, contrary to the desire to produce more photons per unit LED chip area and to make SSL more affordable. Pending a solution to efficiency droop, an alternative device could be a blue laser diode (LD). LDs, operated in stimulated emission, can have high efficiencies at much higher input power densities than LEDs can. In this article, LEDs and LDs for future SSL are explored by comparing: their current state‐of‐the‐art input‐power‐density‐dependent power‐conversion efficiencies; potential improvements both in their peak power‐conversion efficiencies and in the input power densities at which those efficiencies peak; and their economics for practical SSL. 相似文献
The new comprehensive model of the process for matching epitaxial layers to substrates, in dependence of theirs crystallographic orientation, was developed to allow a theoretical prediction of the strain and stress in thin AlGaN epitaxial layers with different composition grown on GaN template. The elements of the continuous anisotropic materials strength theory was applied to develop the model. It was observed that in AlGaN/GaN heterostructures the stress was greater than the upper limit of acceptable tensile stress even for a small Al content and also that the stress could greatly vary, in a value and a direction, depending on substrate crystallographic orientation and an Al content in AlGaN layer. The obtained results theoretically explained the commonly observed technological problems occurring during the growth of AlGaN layers even with a small Al content. 相似文献
High indium semipolar(1122) and polar(0001) In Ga N layers each with a thickness of about 100 nm are realized simultaneously on sapphire substrates by pulsed metal organic chemical vapor deposition(MOCVD). The morphology evolution, structural and optical characteristics are also studied. The indium content in the layer of the surface(1122)is larger than that of the surface(0001), which is confirmed by reciprocal space map, photoluminescence spectrum and secondary ion mass spectrometer. Additionally, the(0001) surface with island-like morphology shows inhomogeneous indium incorporation, while the(1122) surface with a spiral-like morphology shows a better homogeneous In composition.This feature is also demonstrated by the monochromatic cathodoluminescence map. 相似文献