Simultaneous Growth of Various InGaN/GaN Core‐Shell Microstructures for Color Tunable Device Applications

Abstract

An approach to simultaneously grow independent core‐shell structures emitting at different wavelengths by selective area epitaxy is presented. By using seeds of different sizes, the monolithic integration of various GaN crystals including elongated nano‐rods (NRs), micro‐platelets (MPs), and a range of pyramid‐like structures are demonstrated. Dominant non‐polar sidewalls cover more than 75% of the surface area of the NRs, while the polar top facet are about 80% of the total surface of the MPs. InGaN/GaN quantum wells (QWs) deposited on these structures exhibit independent and well‐separated emissions in the green–blue and orange–red ranges, respectively. The pyramid‐like structures at intermediate seed sizes are more complex with semi‐polar facets nearly totaling 60% of the total surface area, resulting in yellow luminescence strongly broadened by the nearby facets contributions. These results suggest the total surface area of each facets and the resulting optical properties of the crystals can be tailored by adjusting the size of the seeds. However, further improvements are required to locally enhance the vertical, pyramidal, and lateral growth of the GaN cores and increase the spectral purity of the different QWs. The approach presented is of interest to design multi‐wavelength devices which requires independent subpixels of high color purity.

Flexible and monolithically integrated multicolor light emitting diodes using morphology-controlled GaN microstructures grown on graphene films

“…The optical characteristics of the GaN microstructure LEDs can be analyzed by comparing them with previously reported result. Robin et al reported simultaneous growth of GaN microrod, micropyramid, and microdisk by controlling the diameter of the growth mask opening and fabricated different LEDs by subsequent deposition of InGaN/GaN QWs on those structures 5 . Their observation of photoluminescence (PL) and cathodo-luminescence (CL) shows the similar tendency to our data demonstrating wavelength shift from blue to green and red as the structure changes from microrod to micropyramid and microdisk.…”

“…Previous integration methods using multiple transfer steps (pick-up and drop-off) onto a flexible substrate and self-assembly limit inorganic LEDs to high-resolution displays and are neither reliable nor reproducible for mass production. The integration issue would be resolved using monolithically integrated micro-LEDs to demonstrate multicolor emissions via tuning their bandgap by varying the In composition of the InGaN/GaN quantum well (QW) [5][6][7] . Meanwhile, recent studies on GaN based micro-and nanostructures on chemical-vapor-deposited (CVD) graphene films have demonstrated their suitability for flexible light-emitting-device applications 8,9 .…”

A Decade of Nonpolar and Semipolar III-Nitrides: A Review of Successes and Challenges

“…By varying the pitch size on a wafer, LEDs with different emission colors can be obtained . In addition, Robin et al recently reported a strong dependence of nonpolar and semipolar surface contribution to the nanostructures on the seed size in the selective‐area epitaxy. A controlled wide range of emission colors from blue to red was obtained for InGaN/GaN QWs grown on these nanostructures by tuning the pattern opening and the resulting seed size, which is promising for obtaining RGB subpixels required for color tunable devices.…”

Nano-LED induced chemical reactions for structuring processes

“…The exploitation of these materials with their unique properties opens the way to a broad range of new devices resulting in applications and solutions in physics, chemistry, biology or medicine. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] However, before they can be fabricated industrially, structuring techniques have to be developed which allow the production of nanostructured materials reproducibly, in a short time and with a high yield. It is the precondition for successful future nanotechnology.…”