Blue and Green InGaN Quantum Well Structure LEDs

III-V nitride films were grown by the two-flow metalorganic chemical vapour deposition (MOCVD) method, details of which are described elsewhere [1]. The growth was conducted at atmospheric pressure. Sapphire with (0001) orientation (C-face), of two-inch diameter, was used as a substrate. 

FIGURE 3 EL of green SQW LEDs with various forward currents. 

The typical output power and external quantum efficiency of the UV LEDs were 5 mW and 7.5%, which were about five times higher than those of previously reported UV InGaN/ AlGaN DH LEDs at a current of 20 mA [1,13-15], The peak wavelength and the full-width at half-maximum (FWHM) of the emission spectra were 371 nm and 8.6 nm, respectively. The peak wavelength (371 nm) is much shorter than that (400 nm) of previous UV LEDs, which is much better for exciting phosphors. 

FIGURE 4 shows the output power as a function of the emission wavelength [3], 

This is probably related to the deep localised energy states which were caused by the In composition fluctuations of the InGaN active layer due to a phase separation during growth [20-23], 

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C3.1 UV, blue and green InGaN quantum well structure LEDs... 

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