High-efficiency and crack-free ingan-based leds on a 6-inch si (111) substrate with a composite buffer layer structure and quaternary superlattices electron-blocking layers

In this paper, a composite buffer layer structure (CBLS) with multiple AlGaN layers and grading of Al composition/u-GaN1/(AlN/GaN) superlattices/u-GaN2 and InAlGaN/AlGaN quaternary superlattices electron-blocking layers (QSLs-EBLs) are introduced into the epitaxial growth of InGaN-based light-emitting diodes (LEDs) on 6-inch Si (111) substrates to suppress cracking and improve the crystalline quality and emission efficiency. The effect of CBLS and QSLs-EBL on the crystalline quality and emission efficiency of InGaN-based LEDs on Si substrates was studied in detail. Optical microscopic images revealed the absence of cracks and Ga melt-back etching. The atomic force microscopy images exhibited that the root-mean-square value of the surface morphology was only 0.82 nm. The full widths at half maxima of the (0002) and $(10\ overline{1}2)$ reflections in the double crystal X-ray rocking curve were ${\sim}{330}$ and 450 arcs, respectively. The total threading dislocation density, revealed by transmission electron microscopy, was < × 10⁸ cm^-2. From the material characterizations, described above, blue and white LEDs emitters were fabricated using the epiwafers of InGaN-based LEDs on 6-inch Si substrates. The blue LEDs emitter that comprised blue LEDs chip and clear lenses had an emission power of 490 mW at 350 mA, a wall-plug efficiency of 45% at 350 mA, and an efficiency droop of 80%. The white LEDs emitter that comprised blue LEDs chip and yellow phosphor had an emission efficiency of ∼ 110 lm/W at 350 mA and an efficiency droop of 78%. These results imply that the use of a CBLS and QSLs-EBL was found to be very simple and effective in fabricating high-efficiency InGaN-based LEDs on Si for solid-state lighting applications.