![]() ![]() Figure 2(e) shows the cross-sectional and top-view (inset) SEM images after vertical GaN growth at low temperature and high pressure, revealing that the SiO 2 mask formed on the PSS pattern prevented the GaN from forming a seed layer. Figure 2(d) presents an energy-dispersive x-ray (EDX) mapping image of the obtained surface prior to GaN deposition in which the blue dots represent silicon. This image clearly demonstrates that the SiO 2 remained on the lenses after removal of the photoresist mask and the SiO 2 deposited thereon. Figure 2(c) shows an SEM image of a SiO 2 mask grown to ∼100 nm on an etched photoresist mask. įigures 2(a) and 2(b) present the SEM images of the photoresist coated on the PSS/AlN before and after O 2 plasma etching, respectively, where the degree of exposure of the PSS pattern is dependent on the height of the remaining photoresist. However, the growth of the pattern affects templates grown epitaxially, which can reduce the overall crystalline quality. As various planes exist in the PSS pattern, the active layer must be grown on the bottom. In these systems, the light generated in the active layer is reflected from the PSS to improve light efficiency. 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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