Enhanced Light Output Power on Near-Infrared Light-Emitting Diodes with TITO/Ag Multilayer Reflector.

A titanium-indium tin oxide (TITO) multilayer reflector was investigated to improve the light efficiency of high-power, near-infrared, light-emitting diodes (NIR-LEDs). The TITO/Ag was fabricated by combining a patterned TITO and an omnidirectional reflector (ODR). For fabricating a high-power NIR-LED, the wafer bond process required the TITO reflective structure, which has patterns filled by AlAu contact metal, bonded directly to the Ag reflector deposited on the silicon wafer. Among Ag-based single- and multilayer reflectors, the TITO/Ag showed the highest reflectance (R = 96%), which was favorable for wafer-bonded high-power NIR-LEDs. Therefore, the TITO/Ag reflector enabled the production of wafer-bonded NIR-LED chips that exhibit superior output performance (190 mW) compared with conventional cases using a single Ag reflector.

Demonstration of Efficient Ultrathin Side-Emitting InGaN/GaN Flip-Chip Light-Emitting Diodes by Double Side Reflectors.

This work proposes an InGaN/GaN multiple-quantum-well flip-chip blue ultrathin side-emitting (USE) light-emitting diode (LED) and describes the sidewall light emission characteristics for the application of backlight units in display technology. The USE-LEDs are fabricated with top (ITO/distributed Bragg reflector) and bottom (Ag) mirrors that cause light emission from the four sidewalls in a lateral direction. The effect of light output power (LOP) on lateral direction is consistently investigated for improving the optoelectronic performances of USE-LEDs. Initially, the reference USE-LED suffers from very low LOP because of poor light extraction efficiency (LEE). Therefore, the LEE is improved by fabricating ZnO nanorods at each sidewall through hydrothermal method. The effects of ZnO nanorod lengths and diameters on LOP are systematically investigated for optimizing the dimensions of ZnO nanorods. The optimized ZnO nanorods improve the LEE of USE-LED, which thus results in increasing the LOP > 80% compared to the reference LED. In addition, the light-tools simulator is also used for elucidating the increase in LEE of ZnO nanorods USE-LED.

32 × 32 Pixelated High-Power Flip-Chip Blue Micro-LED-on-HFET Arrays for Submarine Optical Communication.

This work proposes the use of integrated high-power InGaN/GaN multiple-quantum-well flip-chip blue micro light-emitting diode (µ-LED) arrays on an AlGaN/GaN-based heterojunction field-effect transistor (HFET), also known as a high electron mobility transistor (HEMT), for various applications: underwater wireless optical communication (UWOC) and smart lighting. Therefore, we demonstrate high-power µ-LED-on-HEMT arrays that consist of 32 × 32 pixelated µ-LED arrays and 32 × 32 pixelated HEMT arrays and that are interconnected by a solder bump bonding technique. Each pixel of the µ-LED arrays emits light in the HEMT on-state. The threshold voltage, the off-state leakage current, and the drain current of the HEMT arrays are -4.6 V, <~1.1 × 10-9 A at gate-to-source voltage (VGS) = -10 V, and 21 mA at VGS = 4 V, respectively. At 12 mA, the forward voltage and the light output power (LOP) of µ-LED arrays are ~4.05 V and ~3.5 mW, respectively. The LOP of the integrated µ-LED-on-HEMT arrays increases from 0 to ~4 mW as the VGS increases from -6 to 4 V at VDD = 10 V. Each pixel of the integrated µ-LEDs exhibits a modulated high LOP at a peak wavelength of ~450 nm, showing their potential as candidates for use in UWOC.

Effect of Thermal Interface Materials on Heat Dissipation of Light-Emitting Diode Headlamps with Thermally-Conductive Plastics.

We study the effect of thermal interface material such as thermal-conductive plastic on the dissipation of generated heat from the light-emitting diodes (LEDs) based headlamp for the application of environment-friendly green energy in vehicles. The thermal distribution and the performances of thermal-conductive plastic with heatsink are consistently investigated by using experimental and numerical results. Various thicknesses of thermal-conductive plastics from 0.3 mm to 1.0 mm used in this research work. Basically the thermal-conductive plastic reduces the thermal interface resistance between the contact of two solid surfaces. As a result, High electrical power of about 15 W (1 A and 15 V) can be possible for applying to the high-power LED package without any damage. The soldering temperature of LED package without thermal-conductive plastic shows approximately 138.7 °C which is higher compared to the LED package with thermal-conductive plastic (124.3 °C). On the other hand, the soldering temperature increases from 124.3 to 127.6 °C with increasing the thicknesses of thermal-conductive plastic. In addition, the soldering temperature decreases from 138.7 to 124.3 °C with increasing the thermal conductivities of thermal-conductive plastic. Finally, a highly thermal conductive property of thermal-conductive plastic will propose for optimum dissipation of generated heat from the LEDs-based headlamp. We also successfully estimate the junction temperature of packaged LEDs by using soldering temperature.

Influence of the Thermal Conductivity of Thermally Conductive Plastics on the Thermal Distribution of an Light-Emitting Diode Headlight for Vehicles.

This paper investigates the thermal distribution of an LED headlight for vehicles based on the thermal conductivity of thermally conductive plastics (TCP). In general, heat dissipation structures used for LED headlights are made from metallic materials. However, headlight structures made from TCP have not been investigated. The headlights made from TCP having a various thermal conductivity were fabricated by injection molding with and without a metal plate insert. The temperature characteristics were compared and analyzed using thermal simulations and measurement. The inserted metal in TCP greatly reduced the temperature at solder point, indicating that the fast heat dissipation from the high power LED package to TCP though the inserted metal is essential. The measured temperature at solder points decreased as the thermal conductivity of TCP increased, which is well matched to the simulation results. The measured temperature at the solder point was lower than 150 °C when the thermal conductivity of the TCP was 10 W/mK.

Opposite Behavior of Multilayer Graphene/ Indium-Tin-Oxide p-Electrode for Gallium Nitride Based-Light Emitting Diodes Depending on Thickness of Indium-Tin-Oxide Layer.

In order to improve EQE, we have investigated on the role of multilayer graphene (MLG) on the electrical and optical properties of GaN based light-emitting diodes (LEDs) with ultrathin ITO (5 nm or 10 nm)/p-GaN contacts. The MLG was transferred on the ITO/p-GaN to decrease sheet resistance of thin ITO p-electrode and improve the current spreading of LEDs. The LEDs with the ITO 5 nm and MLG/ITO 5 nm structures showed 3.25 and 3.06 V at 20 mA, and 11.69 and 13.02 mW/sr at 400 mA, respectively. After forming MLG on ITO 5 nm, the electro-optical properties were enhanced. Furthermore, the GaN based-LEDs applied to the ITO 10 nm, and MLG/ITO (10 nm) structures showed 2.95 and 3.06 V at 20 mA, and 20.28 and 16.74 mW/sr at 400 mA, respectively. The sheet resistance of the MLG transferred to ITO 5 nm was decreased approximately four fold compared to ITO 5 nm. On the other hand, the ITO 10 nm and MLG/ITO 10 nm showed a similar sheet resistance; the transmittance of the LEDs with ITO 10 nm decreased to 16% due to MLG formation on ITO. This suggests that the relationship between the sheet resistance and transmittance according to the ITO film thickness affected the electro-optical properties of the LEDs with a transparent p-electrode with the MLG/ITO dual structure.

Impact of Plasma Electron Flux on Plasma Damage-Free Sputtering of Ultrathin Tin-Doped Indium Oxide Contact Layer on p-GaN for InGaN/GaN Light-Emitting Diodes.

The origin of plasma-induced damage on a p -type wide-bandgap layer during the sputtering of tin-doped indium oxide (ITO) contact layers by using radiofrequency-superimposed direct current (DC) sputtering and its effects on the forward voltage and light output power (LOP) of light-emitting diodes (LEDs) with sputtered ITO transparent conductive electrodes (TCE) is systematically studied. Changing the DC power voltage from negative to positive bias reduces the forward voltages and enhances the LOP of the LEDs. The positive DC power drastically decreases the electron flux in the plasma obtained by plasma diagnostics using a cutoff probe and a Langmuir probe, suggesting that the repulsion of plasma electrons from the p -GaN surface can reduce plasma-induced damage to the p -GaN. Furthermore, electron-beam irradiation on p -GaN prior to ITO deposition significantly increases the forward voltages, showing that the plasma electrons play an important role in plasma-induced damage to the p -GaN. The plasma electrons can increase the effective barrier height at the ITO/deep-level defect (DLD) band of p -GaN by compensating DLDs, resulting in the deterioration of the forward voltage and LOP. Finally, the plasma damage-free sputtered-ITO TCE enhances the LOP of the LEDs by 20% with a low forward voltage of 2.9 V at 20 mA compared to LEDs with conventional e-beam-evaporated ITO TCE.

Improved Heat Dissipation of High-Power LED Lighting by a Lens Plate with Thermally-Conductive Plastics.

The junction temperature of high-power LED lighting was reduced effectively using a lens plate made from a thermally-conductive plastics (TCP). TCP has an excellent thermal conductivity, approximately 5 times that of polymethylmethacrylate (PMMA). Two sets of high-power LED lighting were designed using a multi array LED package with a lens plate for thermal simulation. The difference between two models was the materials of the lens plate. The lens plates of first and second models were fabricated by PMMA (PMMA lighting) and TCP (TCP lighting), respectively. At the lens plate, the simulated temperature of the TCP lighting was higher than that of the PMMA lighting. Near the LED package, the temperature of the TCP lighting was 2 °C lower than that of the PMMA lighting. This was well matched with the measured temperature of the fabricated lighting with TCP and PMMA.

Role of the ABCB1 Drug Transporter Polymorphisms in the Pharmacokinetics of Oseltamivir in Humans: a Preliminary Report.

Oseltamivir is a substrate of P-glycoprotein, an efflux drug transporter encoded by ABCB1. The objective of this study was to assess the role of ABCB1 (c.1236C>T, c.2677G>T/A, and c.3435C>T) polymorphisms in the pharmacokinetics of oseltamivir and its active metabolite, oseltamivir carboxylate in humans. Nineteen healthy male subjects were enrolled, and their ABCB1 polymorphisms were evaluated. After the oral administration of 75 mg oseltamivir, the plasma concentrations of oseltamivir and oseltamivir carboxylate were measured. Pharmacokinetic analysis was carried out. Systemic exposure to oseltamivir and oseltamivir carboxylate was higher in the mutant group than in the wild-type and heterozygous groups. We suggest that ABCB1 polymorphisms affect the pharmacokinetics of oseltamivir in humans. Further studies in a large population are necessary to validate the results of this preliminary study (Clinical Trial Registration Information [CRIS] registry: http://cris.nih.go.kr, No. KCT0001903).

Electron beam irradiated silver nanowires for a highly transparent heater.

Transparent heaters have attracted increasing attention for their usefulness in vehicle windows, outdoor displays, and periscopes. We present high performance transparent heaters based on Ag nanowires with electron beam irradiation. We obtained an Ag-nanowire thin film with 48 ohm/sq of sheet resistance and 88.8% (substrate included) transmittance at 550 nm after electron beam irradiation for 120 sec. We demonstrate that the electron beam creates nano-soldering at the junctions of the Ag nanowires, which produces lower sheet resistance and improved adhesion of the Ag nanowires. We fabricated a transparent heater with Ag nanowires after electron beam irradiation, and obtained a temperature of 51 °C within 1 min at an applied voltage of 7 V. The presented technique will be useful in a wide range of applications for transparent heaters.

Pharmacokinetics and Safety Profile of DA-3803, a Proposed Biosimilar of Recombinant Human Chorionic Gonadotropin, in Healthy Subjects.

BACKGROUND AND OBJECTIVE: DA-3803 is a proposed biosimilar of recombinant human chorionic gonadotropin (r-hCG), which is a therapeutic protein used to treat infertility. We compared the pharmacokinetics and safety profiles of DA-3803 (test) with those of a conventional formulation (Ovidrel(®), reference). METHODS: A single-blind, randomized, single-dose, two-period, two-sequence, crossover study was conducted in 32 healthy subjects. In each period, 250 µg of r-hCG of the test or reference formulation was administered subcutaneously with a 3-week washout period. Serial blood samples were obtained for pharmacokinetic analysis and blood levels of human chorionic gonadotropin (hCG) were determined. The geometric mean ratios (GMRs) with 90 % confidence intervals (CIs) for the maximum (peak) plasma concentration (C max) and the area under the plasma concentration-time curve (AUC) were estimated. RESULTS: Among the 32 subjects, 27 completed the study. No serious adverse events were observed. The mean concentration-time profiles of the test formulation tended to be higher than those of the reference formulation. The mean C max values of the two products were similar (142 mIU/mL for reference vs. 143 mIU/mL for test), but the mean AUC from time zero to infinity (AUC∞) values of the test drug were approximately 25 % higher than those of the reference drug (9403 mIU·h/mL for reference vs. 11,817 mIU·h/mL for test). The GMR (90 % CI) of the test formulation to the reference formulation for C max, AUC from time zero to the last measurable time (AUClast), and AUC∞ were 1.03 (0.93-1.14), 1.25 (1.18-1.33), and 1.27 (1.19-1.35), respectively. CONCLUSION: A single subcutaneous injection of either DA-3803 or Ovidrel(®) was safe and well-tolerated. A comparative pharmacokinetics study showed that DA-3803 was bioequivalent to Ovidrel(®) in the C max value but non-equivalent in the AUC value. These pharmacokinetic differences may not be expected to affect therapeutic efficacy of these two drugs, but further clinical studies are warranted to confirm their therapeutic equivalence.

Effects of the ABCG2 and ABCB1 drug transporter polymorphisms on the pharmacokinetics of bicalutamide in humans.

BACKGROUNDS: Bicalutamide is an oral non-steroidal anti-androgen used in the treatment of prostate cancer. Drug transporters P-glycoprotein encoded by ABCB1 and breast cancer resistance protein (BCRP) encoded by ABCG2 are involved in the transportation of bicalutamide and its treatment failure. We evaluated the roles of ABCB1 and ABCG2 genetic polymorphisms in the pharmacokinetics of bicalutamide in humans. METHODS: After a single oral dose of 150mg bicalutamide was administered, plasma concentrations of bicalutamide were measured, and pharmacokinetic analyses were performed in 27 healthy subjects according to ABCB1 (c.1236C>T, c.2677G>T/A, and c.3435C>T) and ABCG2 (c.34G>A and c.421C>A). RESULTS: ABCB1 polymorphisms did not affect the plasma levels of bicalutamide and the pharmacokinetic parameters did not differ among ABCB1 genotype groups. However, the ABCG2 c.421C>A polymorphism significantly influenced the plasma levels and pharmacokinetics of bicalutamide gene dose-dependently. CONCLUSIONS: The ABCB1 genetic polymorphisms did not influence the pharmacokinetics of bicalutamide. However, ABCG2 c.421C>A significantly and gene dose-dependently influenced its pharmacokinetics, but c.34G>A did not.

Pharmacokinetics and tolerability of the new second-generation nonnucleoside reverse- transcriptase inhibitor KM-023 in healthy subjects.

BACKGROUND: KM-023 is a new second-generation nonnucleoside reverse-transcriptase inhibitor that is under development for the treatment of human immunodeficiency virus (HIV) type 1 infection. OBJECTIVE: This study determined KM-023 tolerability and pharmacokinetic characteristics in healthy subjects. MATERIALS AND METHODS: A randomized, double-blinded, placebo-controlled, dose-escalation study was conducted in 80 healthy South Korean male volunteers. The subjects were allocated to single- or multiple-dose (once daily for 7 days) groups that received 75, 150, 300, or 600 mg drug or placebo in a 4:1 ratio. Safety and pharmacokinetic assessments were performed during the study. Plasma and urine concentrations were quantified using liquid chromatography-tandem mass spectrometry. RESULTS: The average maximum concentration (Cmax) and area under the concentration-time curve from time 0 to infinity (AUC∞) values of KM-023 for the 75-600 mg doses in the single-dose study ranged from 440.2 ng/mL to 1,245.4 ng/mL and 11,142.4 ng · h/mL to 33,705.6 ng · h/mL, respectively. Values of the mean Cmax at a steady state and AUC within the dosing interval ranged from 385.1 ng/mL to 1,096.7 ng/mL and 3,698.9 ng · h/mL to 10,232.6 ng · h/mL, respectively, following 75-600 mg doses in the multiple-dose study. Dose proportionality was not observed for KM-023. KM-023 showed a 0.6-fold accumulation after multiple doses in the 600 mg dose group. The mean half-life values ranged between 20.7 and 31.2 hours. KM-023 was generally well tolerated without serious adverse events. CONCLUSION: KM-023 demonstrated dose- and time-dependent nonlinear pharmacokinetic characteristics after single or multiple doses over a dose range (75-600 mg) in healthy subjects. KM-023 showed favorable tolerability in this study. This Phase I clinical trial information can be used to design further clinical studies appropriately to evaluate KM-023 in patients with HIV-1 infection.

Sustained Increase in the Oral Bioavailability of Loperamide after a Single Oral Dose of HM30181, a P-glycoprotein Inhibitor, in Healthy Male Participants.

HM30181 is a new P-glycoprotein (P-gp) inhibitor. This study was conducted to investigate the effect of HM30181 and its duration of action on P-gp inhibition using loperamide as a probe drug. An open-label, five-period, fixed-sequence, cross-over study was conducted in 25 healthy Korean participants, who received a single oral dose of loperamide at 16 mg in five periods lasting for 17 days. In period II, participants also randomly received a single oral dose of HM30181 at 1, 5, 10, 15 mg simultaneously with loperamide. Serial pharmacokinetic blood samples were obtained up to 72 and 336 hr after loperamide and HM30181 administration, respectively. A mixed-effects analysis was performed to compare the area under the plasma concentration versus time curve from time 0 to 72 hr (AUC0-72 hr ) between periods and HM30181 dose groups. Tolerability was also assessed. The AUC0-72 hr of repeatedly administered loperamide was significantly increased 1.18-1.62 times for up to 14 days after a single oral administration of HM30181, particularly at doses ≥10 mg although the between-group difference failed to reach statistical significance. Plasma HM30181 was not detected in many participants including none at any sampling points beyond 48 hr after administration. Most adverse events (AEs) were mild to moderate and resolved spontaneously. The oral bioavailability of loperamide was significantly enhanced by a single oral administration of HM30181, which was sustained for up to 14 days. HM30181 was well tolerated in this selected population.