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

Abstract

Near-Ultraviolet (NUV) and violet light-emitting diodes (LEDs) with an In Ga Nmulti-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 <1120>GaN direction or the <1100> GaN direction was fabricated by standard photolithography and subsequent reactive ion etching (RIE). In this study, the PSS with parallel grooves along the <1120>GaN direction was used. The GaN layer grown by lateral epitaxy on a patterned substrate (LEPS) had dislocation density of 1.5x108 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 (P0) 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. © 2003, The Illuminating Engineering Institute of Japan. All rights reserved.