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

Abstract

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-meansquare value of the surface morphology was only 0.82 nm. The full widths at half maxima of the (0002) and (1012) reflections in the double crystal X-ray rocking curve were ∼330 and 450 arcs, respectively. The total threading dislocation density, revealed by transmission electron microscopy, was <6 × 10 8 cm −2 . From the material characterizations, described above, blue and white LEDs emitters were fabricated using the epiwafers of InGaNbased 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 Manuscript 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.Index Terms-GaN, composite buffer layer structure, quaternary superlattices EBL, Si substrate, MOCVD, light-emitting diodes (LEDs).

A comparative study of efficiency droop and internal electric field for InGaN blue lighting-emitting diodes on silicon and sapphire substrates

“…Silicon has been considered as an attractive substrate material for LEDs because of its inexpensive large-sized wafers. Several groups have reported high-performance GaN-based LEDs grown on silicon substrates overcoming the large mismatch in the lattice constant and thermal expansion coefficients between GaN and silicon 18 19 20 21 , and the successful commercialization of GaN LEDs on silicon substrates is expected to be realized in the near future. However, the efficiency droop of InGaN LEDs on silicon substrates have been relatively unexplored compared to the extensive results on the efficiency droop of InGaN LEDs on sapphire substrates.…”

Efficiency Droop and Effective Active Volume in GaN-Based Light-Emitting Diodes Grown on Sapphire and Silicon Substrates

“…The growth of InGaN/GaN layers on silicon substrates has attracted great interest because of the low substrate cost and the availability of large size wafers. High-performance GaN-based blue LEDs on silicon have been achieved by overcoming the technological difficulty in their growth caused by the large mismatch in the lattice constant and the thermal expansion coefficients between silicon and GaN [7][8][9][10][11].…”