A lighting device comprising first and second groups of solid state light emitters, which emit light having peak wavelength in ranges of from 430 nm to 480 nm, and first and second groups of lumiphors which emit light having dominant wavelength in the range of from 555 nm to 585 nm. In some embodiments, if current is supplied to a power line, a combination of (1) light exiting the lighting device which was emitted by the first group of emitters, and (2) light exiting the lighting device which was emitted by the first group of lumiphors would have a correlated color temperature which differs by at least 50 K from a correlated color temperature which would be emitted by a combination of (3) light exiting the lighting device which was emitted by the second group of emitters, and (4) light exiting the lighting device which was emitted by the second group of lumiphors.

Lighting device and lighting method

A nitride semiconductor light-emitting device has an active layer of a single-quantum well structure or multi-quantum well made of a nitride semiconductor containing indium and gallium. A first p-type clad layer made of a p-type nitride semiconductor containing aluminum and gallium is provided in contact with one surface of the active layer. A second p-type clad layer made of a p-type nitride semiconductor containing aluminum and gallium is provided on the first p-type clad layer. The second p-type clad layer has a larger band gap than that of the first p-type clad layer. An n-type semiconductor layer is provided in contact with the other surface of the active layer.

Nitride semiconductor light emitting device

We fabricated three types of high luminous efficacy white light emitting diodes (LEDs). The first was a white LED with a high luminous efficacy (?L) of 249?lm?W?1 and a high luminous flux (v) of 14.4?lm at a forward-bias current of 20?mA. This ?L was approximately triple that of a tri-phosphor fluorescent lamp (90?lm?W?1). The blue LED used as the excitation source in this white LED had a high output power (e) of 47.1?mW and a high external quantum efficiency (?ex) of 84.3%. The second was a high-power white LED, fabricated from the above high-power blue LED, and had a high e of 756?mW at 350?mA. v and ?L of the high-power white LED were 203?lm and 183?lm?W?1 at 350?mA, respectively. The third was a high-power white LED fabricated from four high-power blue LED dies. v and ?L of the high-power white LED were 1913?lm and 135?lm?W?1 at 1?A, respectively. The white LED had a higher flux than a 20?W-class fluorescent lamp and 1.5 times the luminous efficacy of a tri-phosphor fluorescent lamp (90?lm?W?1).

https://iopscience.iop.org/article/10.1088/0022-3727/43/35/354002/pdf

White light emitting diodes with super-high luminous efficacy

Provided is a light emitting diode (LED) manufactured by using a wafer bonding method and a method of manufacturing a LED by using a wafer bonding method. The wafer bonding method may include interposing a stress relaxation layer (33) formed of a metal between a semiconductor layer (20) and a bonding substrate (31). When the stress relaxation layer is used, stress between the bonding substrate and a growth substrate may be offset due to the flexibility of metal, and accordingly, bending or warpage of the bonding substrate may be reduced or prevented.

Light-emitting device and method of manufacturing the same

The need for efficient, compact and robust solid-state UV optical sources and sensors had stimulated the development of optical devices based on III–nitride material system. Rapid progress in material growth, device fabrication and packaging enabled demonstration of high efficiency visible-blind and solar-blind photodetectors, deep-UV light-emitting diodes with emission from 400 to 250 nm, and UV laser diodes with operation wavelengths ranging from 340 to 350 nm. Applications of these UV optical devices include flame sensing; fluorescence-based biochemical sensing; covert communications; air, water and food purification and disinfection; and biomedical instrumentation. This paper provides a review of recent advances in the development of UV optical devices. Performance of state-of-the-art devices as well as future prospects and challenges are discussed.

https://iopscience.iop.org/article/10.1143/JJAP.44.7191/pdf

III-Nitride UV Devices

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 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 1.5×108 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.

https://iopscience.iop.org/article/10.1143/JJAP.40.L583/pdf

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

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 x 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 forward-biased 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.

Concaves and convexes 1 a are formed by processing the surface layer of a first layer 1, and second layer 2 having a different refractive index from the first layer is grown while burying the concaves and convexes (or first crystal 10 is grown as concaves and convexes on crystal layer S to be the base of the growth, and second crystal 20 is grown, which has a different refractive index from the first crystal). After forming these concavo-convex refractive index interfaces 1 a (10 a), an element structure, wherein semiconductor crystal layers containing a light-emitting layer A are laminated, is formed. As a result, the light in the lateral direction, which is generated in the light-emitting layer changes its direction by an influence of the concavo-convex refractive index interface and heads toward the outside. Particularly, when an ultraviolet light is to be emitted using InGaN as a material of a light-emitting layer, a quantum well structure is employed and all the layers between the quantum well structure and the low temperature buffer layer are formed of a GaN crystal, removing AlGaN. The quantum well structure preferably consists of a well layer made of InGaN and a barrier layer made of GaN, and the thickness of the barrier layer is preferably 6 nm–30 nm.

GaN group semiconductor light-emitting element with concave and convex structures on the substrate and a production method thereof

A semiconductor base material, comprising a substrate (1) having an irregular epitaxial growth surface shown in Fig. 1 (a), wherein, when the vapor phase epitaxial growth of GaN crystals is performed, the irregular surface suppresses a lateral growth and promotes a growth in C-axis direction so as to form a base surface allowing a facet surface to be formed thereon and, as shown in Fig. 1 (b), the crystals having the facet surface formed thereon grow on projected parts and also on recessed parts and, when the crystal growth is further performed, the films grown from the projected and recessed parts are connected to each other to eventually cover the irregular surface as shown in Fig. 1 (c) for flattening and, in this case, and area with low dislocation density is formed at the top parts of the projected parts having the facet surface formed thereon to increase the quality of the film.

Semiconductor base material and method of manufacturing the material

PROBLEM TO BE SOLVED: To eliminate various problems which result from the use of a mask layer, and to simplify a manufacturing process. SOLUTION: As shown in Fig. (a), a substrate 1 having an uneven growth face is prepared. When conducting a vapor phase growth using this substrate, the uneven shape of the growth face suppresses the lateral growth, while accelerating the growth in the C axis direction, making the uneven growth face advantageous as a foundation face for forming a facet surface. Consequently, as shown in Fig. (b), crystals are grown on the projecting parts formed with the facet surfaces, while made to grow in the recessed parts also. In the crystal growth is continued, films grown from the projecting parts and recessed parts are jointed together and flattened, while covering the uneven face as shown in Fig. (c). In this case, low-displacement regions are formed in the upper parts of the projecting parts formed with the facet surfaces, and a high-quality film can be manufactured. COPYRIGHT: (C)2002,JPO

Takashi Tsunekawa

Papers

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

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

GaN group semiconductor light-emitting element with concave and convex structures on the substrate and a production method thereof

Semiconductor base material and method of manufacturing the material

Semiconductor substrate and method of manufacturing the same