Crack-free InGaN multiple quantum wells (MQWs) light-emitting diodes with embedded electrode structures (EE-LEDs) were transferred from Si (111) substrate onto the electroplating copper submount. Crystalline quality was investigated by the high resolution x-ray diffraction (HR-XRD) measurement, in which no obvious deteriorations were found in the MQWs structure after the LEDs transferred from silicon substrate onto copper except for a partial residual strain relaxation in the film. The strain relaxation after silicon removal leads to a reduction in quantum confined stark effect (QCSE), which results in the enhancement of internal quantum efficiency (IQE). In comparison to the conventional LEDs on silicon substrate, the light output of the EE-LEDs on copper was enhanced by 122% at an injection current of 350 mA. Besides the enhancement of IQE, the improvement is also attributed to the following factors: the removal of the absorptive substrate, the inserting of the metal reflector between the EE-LEDs structure and the copper submount, the elimination of the electrode-shading, and the rough surface of the exposed AlN buffer layer.

Large reservoirs along rivers regulate downstream flows to generate hydropower but may also store water for irrigation and urban sectors. Reservoir management therefore becomes critical, particularly for transboundary basins, where coordination between riparian countries is needed. Reservoir management is even more important in semiarid regions where downstream water users may be totally reliant on upstream reservoir releases. If the water resources are shared between upstream and downstream countries, potentially opposite interests arise as is the case in the Syrdarya river in Central Asia. In this case study, remote sensing data (radar altimetry and optical imagery) are used to highlight the potential of satellite data to monitor water resources: water height, areal extent and storage variations. New results from 20 years of monitoring using satellites over the Syrdarya basin are presented. The accuracy of satellite data is 0.6 km 3 using a combination of MODIS data and satellite altimetry, and only 0.2 km 3 with Landsat images representing 2-4% of average annual reservoir volume variations in the reservoirs in the Syrdarya basin. With future missions such as Sentinel-3A (S3A), Sentinel-3B (S3B) and surface water and ocean topography (SWOT), significant improvement is expected. The SWOT mission's main payload (a radar interferometer in Ka band) will furthermore provide 2D maps of water height, reservoirs, lakes, rivers and floodplains, with a temporal resolution of 21 days. At the global scale, the SWOT mission will cover reservoirs with areal extents greater than 250 × 250 m with 20 cm accuracy.

We demonstrate the fabrication of hexagonal nano-pillar arrays at the surface of GaN-based light-emitting diodes (LEDs) by nanosphere lithography. By varying the oxygen plasma etching time, we could tune the size and shape of the pillar. The nano-pillar has a truncated cone shape. The nano-pillar array serves as a gradual effective refractive index matcher, which reduces the reflection and increases light cone. It is found that the patterned surface absorbs more pumping light. To compare extraction efficiencies of LEDs, it is necessary to normalize the photoluminescence power spectrum with total absorption rate under fixed pumping power, then we could obtain the correct enhancement factor of the photoluminescence extraction efficiency and optimized structure. The highest enhancement factor of the extraction efficiency is 10.6.

In the paper, a fast coalescence growth is introduced to the epitaxial growth of GaN on silicon substrate. With the fast coalescence growth method, a thin low pressure GaN (LP-GaN) layer used as a function layer, the GaN film could coalesce quickly within a thin thickness, additionally, a smooth surface and high crystal quality could be achieved. With further investigation, it was found that the general GaN coalescence thickness was mainly influenced by the thickness and the growth pressure of the LP-GaN interlayer. And the LP-GaN interlayer has a critical thickness, if over the critical thickness, the crystal quality would degrade. At the same time, it is found that the GaN quality was not affected by the coalescence thickness with a thin LP-GaN interlayer under critical thickness.

In this work, the influence of the V/III ratios of the low temperature (LT) AlN interlayer on GaN grown on Si<111> substrate have been investigated. It was found that V/III ratio of LT-AlN interlayer is another important growth parameter, which the crystalline quality of GaN was strongly dependent on. By optimizing the V/III ratio of LT-AlN, the high quality crack-free GaN epilayer with lower dislocation density on Si substrate have been obtained. We attribute it to the different LT-AlN surface morphology originated from optimizing the V/III ratio. Different V/III ratios could result in different GaN growth rates in vertical and lateral direction, which could effectively prevent the threading dislocation from penetrating through the LT-AlN interlayer.