Strain-induced quantum dots (QDs) like island formations are demonstrated to effectively suppress pits/dislocation generation in high indium content (26.8%) InGaN active layers.In addition to the strain redistribution...Strain-induced quantum dots (QDs) like island formations are demonstrated to effectively suppress pits/dislocation generation in high indium content (26.8%) InGaN active layers.In addition to the strain redistribution in the QD-like islands,strain modulation on the InGaN active layers by using the GaN island capping is employed to form an increased surface potential barrier around the dislocation cores,which inhibits the carrier transport to the surrounding dislocations.Cathodoluminescence shows distinct double-peak emissions at 503nm and 444nm,corresponding to the In-rich QD-like emission and the normal quantum well emission,respectively.The QD-like emission becomes dominated in photoluminescence due to the carrier localization effect of In-rich InGaN QDs at relatively low “carrier injection current”.Accordingly,green emission may be enhanced by the following origins:(1) reduction in pits/dislocations density,(2) carrier localization and strain reduction in QDs,(3) strain modulation by GaN island capping,(4) enhanced light extraction with faceted GaN islands on the surface.展开更多
Precipitates in undoped GaN epilayers with specular surfaces grown on sapphire substrates were imaged by super high-resolution electron microscopy(HREM)and analyzed by energy-dispersive x-ray spectrometry(EDXS).The HR...Precipitates in undoped GaN epilayers with specular surfaces grown on sapphire substrates were imaged by super high-resolution electron microscopy(HREM)and analyzed by energy-dispersive x-ray spectrometry(EDXS).The HREM images of the precipitates appeared more or less hexagonal intersection with several ten-nanometer large,which is the same as that of the V-shape defects.The EDXS spectra of the precipitates were mainly composed of the characteristic x-rays of oxygen,carbon,and gallium elements.The results suggest that the precipitates nucleate at the pinholes of the V-shape cavities and grow as the GaN growth.展开更多
Fine structure in the electron emission process for DX(Sn)centers in AlGaAs has been studied with high resolution Laplace defect spectroscopy.The influence of the different local configuration of Al and Ga atoms aroun...Fine structure in the electron emission process for DX(Sn)centers in AlGaAs has been studied with high resolution Laplace defect spectroscopy.The influence of the different local configuration of Al and Ga atoms around the centers on the electron thermal emissions was observed.An experimental evidence for the microscopic structure of two DX-like centers in Sn-doped AlGaAs is provided.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 60876008 and 61076091the Program for New Century Excellent Talents in Fujian Province University.
文摘Strain-induced quantum dots (QDs) like island formations are demonstrated to effectively suppress pits/dislocation generation in high indium content (26.8%) InGaN active layers.In addition to the strain redistribution in the QD-like islands,strain modulation on the InGaN active layers by using the GaN island capping is employed to form an increased surface potential barrier around the dislocation cores,which inhibits the carrier transport to the surrounding dislocations.Cathodoluminescence shows distinct double-peak emissions at 503nm and 444nm,corresponding to the In-rich QD-like emission and the normal quantum well emission,respectively.The QD-like emission becomes dominated in photoluminescence due to the carrier localization effect of In-rich InGaN QDs at relatively low “carrier injection current”.Accordingly,green emission may be enhanced by the following origins:(1) reduction in pits/dislocations density,(2) carrier localization and strain reduction in QDs,(3) strain modulation by GaN island capping,(4) enhanced light extraction with faceted GaN islands on the surface.
基金Supported in part by the National Natural Science Foundation of China under Grant No.69576022Natural Science Foundation of Fujian Provincethe Research Funds of Japan Society for the Future Program on "Atomic Scale Surface and Interface Dynamics".
文摘Precipitates in undoped GaN epilayers with specular surfaces grown on sapphire substrates were imaged by super high-resolution electron microscopy(HREM)and analyzed by energy-dispersive x-ray spectrometry(EDXS).The HREM images of the precipitates appeared more or less hexagonal intersection with several ten-nanometer large,which is the same as that of the V-shape defects.The EDXS spectra of the precipitates were mainly composed of the characteristic x-rays of oxygen,carbon,and gallium elements.The results suggest that the precipitates nucleate at the pinholes of the V-shape cavities and grow as the GaN growth.
基金Supported by the National Natural Science Foundation of China under Grant No.69576022Natural Science Foundation of Fujian Province of China。
文摘Fine structure in the electron emission process for DX(Sn)centers in AlGaAs has been studied with high resolution Laplace defect spectroscopy.The influence of the different local configuration of Al and Ga atoms around the centers on the electron thermal emissions was observed.An experimental evidence for the microscopic structure of two DX-like centers in Sn-doped AlGaAs is provided.
