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. In this study, the PSS with parallel grooves along the 1120 sapphire direction was fabricated by standard photolithography and subsequent reactive ion etching (RIE). The GaN layer grown by lateral epitaxy on a patterned substrate (LEPS) has a dislocation density of 1.5 × 10 8 cm −2 . The LEPS-UV-LED chips were mounted on the Si bases in a flip-chip bonding arrangement. When the LEPS-UV-LED was operated at a forward-bias 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-bias current, the output power increased linearly and was estimated to be approximately 38 mW at 50 mA.

Analysis of parasitic cyan luminescence occurring in GaInN blue light-emitting diodes J. Appl. Phys. 112, 074512 (2012) Gallium nitride-based light-emitting diodes with embedded air voids grown on Ar-implanted AlN/sapphire substrate Appl. Phys. Lett. 101, 151103 (2012) Analysis of the external and internal quantum efficiency of multi-emitter, white organic light emitting diodes

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.

No abstract

Optical properties of InxGa1−xN epitaxial layers with various indium compositions (x=0.02, 0.03, 0.05, 0.06, and 0.09) have been studied by means of temperature-dependent optical absorption and photoluminescence spectroscopy. A clear peak due to the absorption of InxGa1−xN ternary alloys was observed up to 300 K, which enabled us to investigate the temperature dependence of the Stokes shift. The Stokes shift at 4 K increased with an increase in the indium composition, and was estimated to be 22 and 45 meV for the samples with x=0.02 and 0.09, respectively. With an increase in temperature up to about 50 K, the Stokes shift increased slightly. With a further increase in temperature from 50 to 100 K, the Stokes shift decreased. Above 100 K, the Stokes shift was independent of the temperature and showed an almost constant value up to 300 K. The Stokes shift at 300 K was estimated to be 19 and 34 meV for the samples with x=0.02 and 0.09, respectively. This temperature dependence of the Stokes shift was characteristically common to all of the samples used in the present work, and was observed to be more prominent for the samples with higher indium compositions.