![]() In an effort to enhance the light extraction and efficiency, many researchers have switched from flat sapphire substrates to patterned sapphire substrates (PSSs). ![]() The wavelength generated by the active layer is extracted from the inside of the chip or trapped inside to be converted into thermal energy with a concomitant reduction in light efficiency. In particular, GaN, aluminum nitride (AlN), and indium nitride (InN) can be used in the active layer of LED chips to modulate the LED emission wavelength from the visible to the UV regions and thus obtain light sources with the desired wavelengths. where the latter method is mainly employed in the fabrication of LED chips. The most common techniques used to deposit III-nitrides are molecular beam epitaxy and metalorganic chemical vapor deposition (MOCVD), 10,11 10. In recent years, the use of buffer layers based on relatively inexpensive silicon has been actively investigated for the growth of III-nitrides on large-scale substrates. (98)00437-1 Although sapphire and SiC substrates with lattice constants similar to III-nitrides are expensive, they are still currently used for applications such as light-emitting diodes (LEDs) 5 5. Compound semiconductors based on III-nitride materials, which can typically be easily grown on sapphire, silicon carbide (SiC), and gallium nitride (GaN) substrates, have been extensively studied.
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