Abstract
A micro light-emitting diode (μLED) is a key device for the future of advanced information. Owing to expand its application widely, the concept of the emission-color conversion using layered semiconductors as a color converter is proposed. In addition, it is demonstrated that layered semiconductors were transferred directly onto μLED chips, and the emission-color conversion is realized. The layered GaS1−xSex alloy, whose energy bandgap can be controlled by tuning the S and Se compositions, was selected as a color converter. The photoluminescence (PL) measurements using a blue LED as an excitation source revealed that GaS0.65Se0.35 and GaSe can show green and red luminescence with center energies of 2.34 and 1.94 eV, respectively. The emission color of gallium nitride (GaN)-based blue μLEDs covered with GaS0.65Se0.35 and GaSe thin films were clearly converted to green and red, respectively. Furthermore, the emission color could be controlled by changing the film thickness. Thus, these results suggest the possibility of emission-color conversion of blue μLED chips utilizing layered materials.
Highlights
Micro light-emitting diodes based on gallium nitride (GaN) material systems have received much attention in novel optoelectronic technologies such as next-generation display and wireless communication for the internet of things as well as in interdisciplinary fusion such as biomedical applications [1,2,3]
II-VI based quantum wells (QW) on glass substrates are investigated as the color converter [10,11]
For applications of display and optogenetics, the improvement of light directivity is necessary using an integrated microlens. These results suggest the possibility of emission-color conversion of blue μLED chips utilizing layered materials
Summary
Micro light-emitting diodes (μLEDs) based on gallium nitride (GaN) material systems have received much attention in novel optoelectronic technologies such as next-generation display and wireless communication for the internet of things as well as in interdisciplinary fusion such as biomedical applications [1,2,3]. A head-mounted display for virtual reality, augmented reality and these kinds desire full-color light-emitting devices have been expected as specific application examples. This is because of their properties including high brightness, high response speed, long device lifetime, low power operation, and the realization of microfabrication. Coated phosphors or colloidal quantum dots (QDs) can be realized the emission-color conversion from blue to various visible colors [4,5,6,7,8,9] These color converters should be at least several micrometres (μm) thick because of the realization of high light absorption and high-efficiency luminescence.
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