Blue LED growth from 2 inch to 8 inch

Abstract

Growth of blue InGaN based LED structures on sapphire wafers from 2 inch to 8 inch in diameter was investigated using the Veeco K465 MOCVD platform. Our results indicate that the same pressure, rotation rate and hydride flows can be used for all wafer sizes. AFM and X-ray studies reveal that all wafer sizes have comparable high-quality crystallinity and defect levels for GaN and InGaN/GaN MQW growth. Although the larger diameter wafers exhibit larger wafer bow due to lattice and thermal mismatch, with proper wafer pocket design, good wavelength and thickness uniformity can be obtained for all wafer sizes. GaN, InGaN, blue LED, MOCVD Citation:Lu F, Lee D, Byrnes D, et al. Blue LED growth from 2 inch to 8 inch.

The Science and Practice of Metal-Organic Vapor Phase Epitaxy (MOVPE)

“…With these developments and improved flow modeling capability (discussed in Section 3.4.3, large-scale MOVPE machines have been developed capable of growth on 12 four inch wafers with 90% yield for blue wavelength LEDs [368]. Blue InGaN-based LEDs have been produced on 8-inch sapphire wafers [375]; however, for LED growth on these larger wafers, special care must be taken to reduce wafer curvature [376]. MOVPE systems in the horizontal flow mode or with a close coupled showerhead are also available [374].…”

Control of initial bow of sapphire substrates for III-nitride epitaxy by internally focused laser processing

“…On the other hand, there is a possibility to overcome the large concave shape during the MQW growth stage by accommodating the pocket shape. Therefore, the combination of a concavely pre-bowed sapphire substrate like that of curve (c) and the accommodated wafer carrier pocket shaped like that reported by Amour et al [12] and Lu et al [9] may provide reasonable benefits for the total LED fabrication process; namely, a perfect LED wavelength homogeneity and completely flat surface after cooling for easier chip manufacturing; this is a future challenge.…”

“…They overcame the wavelength uniformity problem by adjusting the shape of the wafer carrier pocket to accommodate the substrate bowing. Lu et al [9] also verified the importance of the wafer carrier design, and good uniformity was reported by accommodating the pocket shape to be the same as the bowing of the sapphire substrate during the InGaN growth stage for diameters up to 200 mm. In addition to the approach using thicker substrates and pocket shape accommodation, epitaxy process optimization, such as modifying the nucleation layer, controlling the coalescence stage, and inserting straincompensation layers, has been reported to reduce the strain and related substrate bowing both during and after epitaxy [10,[13][14][15][16][17][18][19][20][21][22][23].…”

“…As shown by curve (a) in Fig. 6, the standard substrate exhibits a concave shape during the MQW growth stage, which is the reason why Amour et al [12] and Lu et al [9] had to accommodate the pocket shape to the same extent as the bowing of the sapphire substrate to obtain better LED wavelength homogeneity. We achieved a flat substrate shape during the MQW growth stage with the laser-treated, pre-bowed sapphire substrate as shown by curve (b).…”

“…Sapphire substrates are the most common substrates for growing epitaxial layers of III-nitride [8]. The recent trend of sapphire substrates for nitride epitaxy is heading for larger diameter substrates, from 50.8 mm to 100 and 150 mm, due to the strong demand from the LED industry for a reduction of production costs [9]. However, as is well known, the use of larger diameter sapphire substrates in the epitaxy process raises some difficulties because of the increased bowing caused by the large mismatch in the lattice constants and thermal expansion coefficients between sapphire and III-nitride films [10,11].…”