Enhancing the output power of GaN-based LEDs grown on wet-etched patterned sapphire substrates

Improved performance of GaN based light emitting diodes with ex-situ sputtered AlN nucleation layers

“…Moreover, in these two cross-sectional TEM images [ Fig. 3(b) and 3(d)], the g vectors of samples A and B were both g= [11][12][13][14][15][16][17][18][19][20]. The edge-type dislocations were also identified in these two images, which were marked by red circles.…”

“…Among them, patterned sapphire substrates (PSS) are then widely used on GaN based LEDs because the light extraction efficiency can be largely enhanced due to fluctuated interfaces between GaN and sapphire and the TDDs can be well controlled to a certain level to achieve high internal quantum efficiency (IQE). 13 On the other hand, recently developed GaN free-standing substrates can provide excellent crystal quality and benefits of homo-epitaxy in making excellent optoelectronics. 14 However, high material costs of GaN substrates still hold back the popularity of utilizing the GaN substrates.…”

Highly Efficient and Bright LEDs Overgrown on GaN Nanopillar Substrates

“…Due to the large lattice mismatch and thermal expansion coefficient misfit between GaN and sapphire, the subsequent-grown GaN epitaxial layers usually contained high threading dislocation densities (TD densities) (around 10 8 -10 10 cm −2 ) [3]. To improve the crystalline quality of GaN-based epitaxial layers on sapphire substrate, various growth techniques have been proposed, such as epitaxial lateral overgrowth (ELO) [4], [5], cantilever epitaxy (CE) [6], defect selective passivation [7], microscale SiN x or SiO x patterned mask [8]- [10], anisotropically etched GaNsapphire interface [11], plastic relaxation through buried AlGaN cracks [12], and patterned sapphire substrate (PSS) [13]- [15].…”

Improved Output Power of InGaN-Based Ultraviolet LEDs Using a Heavily Si-Doped GaN Insertion Layer Technique

“…Therefore, how to decrease the TDD is an important subject for developing high performance UV-LEDs. Over the past years, several approaches have been proposed for improving the crystalline quality of GaN-based epilayer, such as epitaxial lateral overgrowth (ELOG) [5]- [6], cantilever epitaxy (CE) [7], defect selective passivation [8], microscale SiN x or SiO x patterned mask [9]- [11], and the use of patterned sapphire substrate (PSS) [12]- [14]. However, these methods required additional complex photolithography and etching process.…”