High Output Power Near-Ultraviolet and Violet Light-Emitting Diodes Fabricated on Patterned Sapphire Substrates Using Metalorganic Vapor Phase Epitaxy

Near-Ultraviolet (NUV) and violet light-emitting diodes (LEDs) with an InGaN multi-quantum-well (MQW) structure were fabricated on patterned-sapphire substrate (PSS) using a single growth process of metal-organic vapor phase epitaxy (MOVPE). The PSS with parallel grooves along the GaN direction or the GaN direction was fabricated by standard photolithography and subsequent reactive ion etching (RIE). In this study, the PSS with parallel grooves along the GaN direction was used. The GaN layer grown by lateral epitaxy on a patterned substrate (LEPS) had dislocation density of 1.5×108 cm-2. The LEPS-NUV (or violet)-LED chips were mounted on the Si bases in a flip-chip bonding arrangement. When the LEPS-NUV-LED (the emission peak wavelength λp: 382 nm) was operated at forward-bias current of 20 mA at room temperature, the output power (Ρo) and the external quantum efficiency (ηe) were 15.6 mW and 24%, respectively. When the LEPS-violet-LED (λp: 405 nm) was operated at forward-bias current of 20 mA at room temperature, the output power and the external-quantum efficiency were 26.3 mW and 43%, respectively. The PSS is very effective in reducing the dislocation density and increasing the extraction efficiency in the LEDs because of the scattering of the emission light at the patterned GaN/sapphire interface.