Flexible inorganic-based micro light-emitting diodes (µLEDs) are emerging as a significant technology for flexible displays, which is an important area for bilateral visual communication in the upcoming Internet of Things era. Conventional flexible lateral µLEDs have been investigated by several researchers, but still have significant issues of power consumption, thermal stability, lifetime, and light-extraction efficiency on plastics. Here, high-performance flexible vertical GaN light-emitting diodes (LEDs) are demonstrated by silver nanowire networks and monolithic fabrication. Transparent, ultrathin GaN LED arrays adhere to a human fingernail and stably glow without any mechanical deformation. Experimental studies provide outstanding characteristics of the flexible vertical μLEDs (f-VLEDs) with high optical power (30 mW mm ), long lifetime (≈12 years), and good thermal/mechanical stability (100 000 bending/unbending cycles). The wireless light-emitting system on the human skin is successfully realized by transferring the electrical power f-VLED. Finally, the high-density GaN f-VLED arrays are inserted onto a living mouse cortex and operated without significant histological damage of brain.
We report the InGaN/GaN multiple quantum well vertical light-emitting diodes (VLEDs) operating at λ ∼ 450 nm by the use of laser lift-off and copper electroplating processes. The thermal characteristics of fabricated VLEDs are measured and analyzed in terms of the junction temperature (T j ) using the forward voltage method, which allows us to estimate the thermal resistance (R th ). Between 298 and 378 K, the characteristic temperature is measured to be about 903 K at 350 mA. The far-field patterns of the VLED have a uniform and good near-Lambertian emission. The T j and R th values are also confirmed by the emission peak wavelength shift method. The use of electroplated copper with a high thermal conductivity instead of a sapphire substrate provides much better heat dissipation capability. For a 1 × 1 mm 2 VLED, the low T j value of 305.8 K is obtained with an output power of 191 mW at an injection current of 350 mA at 298 K, exhibiting R th = 7.98 K W −1 .
This paper proposed a novel broadband Planar Inverted-F Antenna(PIFA) for IMT-2000/WLAN/DMB terminal. Two branch lines for meander line were utilized in order to improve the characteristics of PIFA which usually has a narrow band. The shorting strip between the ground plane and meander-type radiation elements were used in order to minimize the size of the antenna. The −10dB return loss bandwidth of a realized antenna was 38.2%(1.84 − 2.71GHz), which contains the broadband bandwidth with triple band. And the simulated and measured values of the 1g and 10g averaged peak SAR on human head caused by the triple band PIFA mounted on folder-type handsets were analyzed and discussed. As a result, the measured 1g and 10g averaged peak SARs of PIFA were similar with the simulated values and were lower than the 1.6W/kg and 2W/kg of the 1g and 10g averaged peak SAR limits.
Non-polar a-plane InGaN/GaN multiple quantum well (MQW) light emitting diodes (LEDs) with different thicknesses and periods of InGaN wells are prepared and characterized. Non-polar a-plane LEDs are grown directly on r-plane sapphire by metalorganic chemical vapor deposition, and LEDs are fabricated. In the electroluminescence (EL) measurements, the relative output power increases slightly with increasing well thickness and the forward operating voltage at 20 mA increases slightly, even though the 4.2 nm thick well exhibits the best photoluminescence (PL) and x-ray diffraction (XRD) results. Although the interface quality degrades with thicker InGaN wells, the relative output power in EL measurement increases due to an increase of carrier capture rate with well thickness. With increasing periods of MQWs up to seven, the relative output power of LEDs is improved due to the increased crystal and interface quality in MQWs. Meanwhile, the forward operating voltage at 20 mA increases from 3.58 to 4.12 V because the series resistance of undoped areas increases with increasing periods of MQWs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.