High Output Power InGaN Ultraviolet Light-Emitting Diodes Fabricated on Patterned Substrates Using Metalorganic Vapor Phase Epitaxy

Abstract

Ultraviolet (UV) light-emitting diodes (LEDs) with an InGaN multi-quantum-well (MQW) structure were fabricated on a patterned sapphire substrate (PSS) using a single growth process of metalorganic vapor phase epitaxy. The GaN layer grown by lateral epitaxy on a patterned substrate (LEPS) has a dislocation density of 1.5 Â 10 8 cm --2 . The LEPS-UV-LED chips were mounted on the Si bases in a flip-chip bonding arrangement. When the UV-LED was operated at a forwardbiased current of 20 mA at room temperature, the emission wavelength, the output power and the external quantum efficiency were estimated to be 382 nm, 15.6 mW and 24%, respectively. With increasing forward-biased current, the output power increased linearly and was estimated to be approximately 38 mW at 50 mA.

Characterization study of GaN-based epitaxial layer and light-emitting diode on nature-patterned sapphire substrate

“…The unique pyramidal morphological pattern on the sapphire surface might have similar functions with current patterned sapphire substrates, i.e., excellent improvements in the GaN epitaxial quality and the light-extraction efficiency for LED devices. [5][6][7][8][9] So, it is of interesting to grow epitaxial GaN/InGaN LED structure on the n-pss wafer with the pyramidal pattern by MOCVD process. The LED epilayer structure includes a 1.8-lm-thick undoped GaN layer and a 2.5-lm-thick Si-doped n-type GaN cladding layer, an active region of 450-nm emitting wavelength with six periods of InGaN/GaN MQWs, and a 0.3-lm-thick Mg-doped p-type GaN cladding layer.…”

“…3,4 The efficacy enhancement of GaN-based LEDs with the patterned-sapphire substrate technique generally attributes to the improvement in both light extraction efficiency and internal quantum efficiency. [5][6][7][8][9] The regular patterns created on the sapphire substrate counteracts the effect of the total internal reflection at the GaN/sapphire interface. 5 And, the enhancement in the internal quantum efficiency benefits from the reduction of threading dislocations by possible lateral growth of GaN epilayer on the patternedsapphire substrate.…”

Anaerobic hydrogen production with an efficient carrier‐induced granular sludge bed bioreactor

“…By the proposed adaptive observer design technique, a chaotic receiver is then derived to recover the information signal at the receiving end of the communication. The transmitter is a chaotic system described by (1) with a slight modification and represented as follows: (6) where s∈R is the information signal and masked by the system's output, and y'∈R is the chaotically transmitted signal, which drives the receiver. Employing the observer-based driven system design, the receiver is constructed as follows: (7) If the system's disturbances and parameters can be exactly estimated by the proposed adaptive scheme from the adaptation phase in which the information signal is set to be zero, i.e.…”

Improving the Light-Emitting Efficiency of GaN LEDs Using Nanoimprint Lithography

“…In addition, these surface structures can display effects similar to the roughened surface to enhance the light extraction efficiency for the multiple reflections at the GaN/sapphire interface as shown in Figure 3, to cause guided light escape to free space while suppressing the TIR. Such substrate patterning is known as the patterned sapphire substrate (PSS) technique [8][9][10][11]. PSS is a popular technique for enhancing LED efficiency.…”