Entity

Time filter

Source Type


Zhang K.,Dalian University of Technology | Liang H.,Dalian University of Technology | Wang D.,Dalian University of Technology | Shen R.,Dalian University of Technology | And 7 more authors.
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2014

The reversed polarization yellow emission InGaN/GaN multiple quantum wells (MQWs) in p-side down (PDMQWs) and n-side down (NDMQWs) structures were grown by metal-organic chemical vapor deposition on sapphire substrates. The properties of PDMQWs in surface morphology, interface quality, optical characteristic, and impurities distribution were investigated and compared with those of NDMQWs. Though degrading the interface abruptness of PDMQWs, the rough surface of p-GaN underlying layer was found to promote InGaN compositional fluctuation or phase separation and the resultant formation of nanodot-like structures with higher In-composition. At the same growth conditions and the similar In-composition for two MQWs, PDMQWs present a longer emission wavelength with an extra emission peak from In-rich nanodot-like structures, compared with that of NDMQWs. Mg memory effect introduces high concentrations of Mg residual in PDMQWs accompanying with the incorporation of C, H, and O impurities, which impose negative influence on the optical properties of PDMQWs. The potentials and problems, as well as the possible problem-solving methods of p-side down light-emitting diodes (PDLEDs) in developing long wavelength emitter were also discussed, which may bring some new thinkings for the design of III-nitrides PDLEDs. © 2014 Elsevier B.V. Source


Wang D.-S.,Dalian University of Technology | Wang D.-S.,Jiangsu Xinguanglian Technology Co. | Guo W.-P.,Jiangsu Xinguanglian Technology Co. | Zhang K.-X.,Dalian University of Technology | And 10 more authors.
Faguang Xuebao/Chinese Journal of Luminescence | Year: 2013

High-performance 400 nm violet InGaN multi-quantum-wells light-emitting diodes (LED) with p-AlGaN electron blocking layer were fabricated on sapphire substrate by metal organic chemical vapor deposition technique. Different kinds of p-AlGaN electron blocking layers were grown in three violet LEDs: bulk p-AlGaN with Al mole fraction of 9%, bulk p-AlGaN with Al mole fraction of 11% and super lattice p-AlGaN/GaN with Al mole fraction of 20%. The output power of violet LED with bulk p-AlGaN(11%) is higher than the LED with bulk p-AlGaN(9%). Typically, the output power of the LED with 10 pairs of p-AlGaN/GaN super lattice electron blocking layer has been greatly improved. A LED with an output power of 21 mW at an injection current of 20 mA is achieved. In additional, the LED also shows an almost linear I-L characteristics at high injection current and uniform intensity mapping on LED chip surface. Source


Tao P.,Dalian University of Technology | Liang H.,Dalian University of Technology | Wang D.,Dalian University of Technology | Xia X.,Dalian University of Technology | And 9 more authors.
Materials Science in Semiconductor Processing | Year: 2014

Crack-free AlGaN/GaN distributed Bragg reflectors (DBRs) for the near-UV region were grown on 6H-SiC substrates by metal-organic chemical vapor deposition (MOCVD). To suppress the generation of cracks, a thin SiNx interlayer was introduced between the first pair of AlGaN/GaN DBR layers. Using this approach, crack-free 30-pair Al0.2Ga0.8N/GaN DBRs were obtained with peak reflectivity of 92.8% at 388 nm and a stop-band bandwidth of 16 nm. Our results reveal that a SiNx interlayer not only decreased the tensile strain but also improved the reflectivity via suppression of cracks. © 2014 Elsevier Ltd. All rights reserved. Source


Tao P.,Dalian University of Technology | Liang H.,Dalian University of Technology | Xia X.,Dalian University of Technology | Liu Y.,Dalian University of Technology | And 7 more authors.
Superlattices and Microstructures | Year: 2015

Near-ultraviolet (UV) InGaN/AlGaN multiple quantum well (MQW) LEDs with 30 pairs AlGaN/GaN distributed Bragg reflectors (DBRs) were grown on 6H-SiC substrate by metal-organic chemical vapor deposition. A thin SiNx interlayer was introduced between the DBRs and n-GaN layer of the LED to reduce the threading dislocation density and result in enhancement the internal quantum efficiency (ηint) of the InGaN/AlGaN LED. The result indicates that the light output power for the LED with DBRs and SiNx interlayer was approximately 56% higher (at 350 mA) than the LED without DBRs and SiNx interlayer on 6H-SiC substrate, and this significant improvement in performance is attributed not only to the light extraction enhancement via the DBRs but also due to improve epilayer crystalline quality. © 2015 Elsevier Ltd. All rights reserved. Source

Discover hidden collaborations