Nearly single-crystalline GaN light-emitting diodes on amorphous glass substrates

Single-crystalline GaN-based light-emitting diodes (s-LEDs) on crystalline sapphire wafers can provide point-like light sources with high conversion efficiency and long working lifetimes. Recently, s-LEDs on silicon wafers have been developed in efforts to overcome the size limitations of the sapphire substrate. However, to create larger, cheaper and efficient flat light sources, the fabrication of high-performance s-LEDs on amorphous glass substrates would be required, which remains a scientific challenge. Here, we report the fabrication of nearly single-crystalline GaN on amorphous glass substrates, in the form of pyramid arrays. This is achieved by high-temperature, predominant GaN growth on a site-confined nucleation layer with preferential polycrystalline morphology through local hetero-epitaxy. InGaN/GaN multiple-quantum wells formed on the GaN pyramid arrays exhibit a high internal quantum efficiency of 52%. LED arrays fabricated using these GaN pyramid arrays demonstrate reliable and stable area-type electroluminescent emission with a luminance of 600 cd m−2.

Figure 1Schematic for fabricating GaN pyramid arrays.

Schematic for fabricating GaN pyramid arrays.
a, Preferential polycrystalline morphology of a titanium pre-orienting layer and a LT-GaN nucleation layer. Both layers have a c-axis preferred orientation in the out-of-plane (z) direction and random orientations in the in-plane (x or…

Figure 2Effect of the presence of a titanium pre-orienting layer on crystallographic orientation of the LT-GaN nucleation layer.

Effect of the presence of a titanium pre-orienting layer on crystallographic orientation of the LT-GaN nucleation layer.
a,b, Bright-field TEM images of LT-GaN, directly grown on a glass substrate (a) and on top of a titanium thin film deposited on a glass substrate (b) reveal the effect of the titanium pre-orienting layer on the (001) preferred growth of…

Figure 3Contour of GaN pyramid arrays formed on the template with hole-patterned SiO2/LT-GaN/titanium/glass.

Contour of GaN pyramid arrays formed on the template with hole-patterned SiO2/LT-GaN/titanium/glass.
GaN pyramid arrays in ae have a dhole value of 2.4 µm. a, Bright-field TEM image of the GaN pyramid showing the predominant and lateral growth mechanism. Inset: selected-area diffraction pattern at the upper part of the pyramid showing…

Figure 4Crystal quality of GaN pyramid arrays and electroluminescence devices fabricated on top of GaN pyramid arrays.

Crystal quality of GaN pyramid arrays and electroluminescence devices fabricated on top of GaN pyramid arrays.
a, Cathodoluminescence spectra of the GaN pyramid arrays formed on glass and sapphire substrates. The former has a peak wavelength of 364 nm with a FWHM of 16 nm (158 meV), and the latter was directly taken from ref. 27and merged with…

SOURECE;Nature

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