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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. [ABSTRACT FROM AUTHOR]

Mg-doped, 1-μm-thick, p-type GaN films were grown by metal-organic chemical vapor deposition using indium-assisted method. The influence of flow rate ratio of indium to magnesium (In/Mg ratio) on the quality of p-GaN thin films was investigated by atomic force microscope, X-ray diffraction, Hall measurement and secondary ion mass spectroscopy. The surface roughness, crystalline quality and hole concentrations of p-GaN present a different variation tendency below and above 0.183 In/Mg ratio. The evolution process of indium-adlayer model considering adsorption, desorption and the transformation of indium mono-adlayer was proposed to explain the above phenomenon. Indium-assisted growth method can improve surface smoothness and crystalline quality of p-GaN effectively without affecting its electrical properties. [ABSTRACT FROM AUTHOR]

Improved structural quality and tensile stress releasing were realized in GaN thin films grown on 6H-SiC by metal organic chemical vapor deposition using an in situ porous SiN interlayer. The SiN was formed in situ in the growth chamber by simultaneous flow of diluted silane and ammonia, leading to the formation of a randomly distributed mask layer and induced lateral overgrowth similar to conventional epitaxial lateral overgrowth of GaN. The full width at half maximum (FWHM) of X-ray diffraction peaks decreases dramatically by the SiN interlayer, indicating an improved crystalline quality. Also, it was found that the biaxial tensile stress in the GaN film was significantly reduced by in situ SiN interlayer from Raman spectra. Low temperature photoluminescence spectra exhibited a narrower FWHM by the SiN interlayer. [ABSTRACT FROM AUTHOR]

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 SiN x interlayer was introduced between the first pair of AlGaN/GaN DBR layers. Using this approach, crack-free 30-pair Al 0.2 Ga 0.8 N/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 SiN x interlayer not only decreased the tensile strain but also improved the reflectivity via suppression of cracks. [ABSTRACT FROM AUTHOR]