Hsiang Chen

Degradation mechanisms in GaN light-emitting diodes undergoing reverse-bias operations in water vapor

Reverse-bias testing light-emitting diodes (LEDs) enables devices to be rapidly screened for weaknesses and pinpoints the origins of failure. In this study, GaN LED reliability was examined by reverse-bias, stressing the device in water vapor. The LED failure origins were investigated using electrical characterizations, optical measurements, and material analyses, namely, focused ion beam deposition, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The results indicated that diffused Au atoms from the surface of the LED can increase leakage current, generate high electric fields, and degrade device performance levels. Moreover, hot-carrier-induced emissions for LEDs undergoing reverse-bias operations confirmed that gold distribution caused by the water vapor generated high electric fields.

Investigation of the CuInSe 2 film prepared by one-step electrodeposition

In this research, we applied one-step electrodeposition to fabricate CuInSe2 films. Deposition parameters, including the pH value of the plating solution, the deposition time and the current density, were adjusted to find preferable conditions to fabricate high quality CuInSe2 film. Material properties were examined by X-ray diffraction (XRD), scanning electron microscope (SEM) images and energy dispersive spectrometer (EDS) analysis. Experimental results indicate that plating solution with a pH value of 1.5, a current density of 0.3 ASD and deposition time of 15 min are the optimal parameters for CuInSe2 film deposition. It is our belief that our findings can further enhance the development of highquality electrodeposited film for use in future copper indium selenide (CIS) solar cell applications.

Ultraviolet GaN Light-Emitting Diodes with Porous-AlGaN Reflectors

A GaN/AlGaN ultraviolet light emitting diode (UV-LED) structure with a porous AlGaN reflector structure has been demonstrated. Inside the UV-LED, the n+-AlGaN/undoped-AlGaN stack structure was transformed into a porous-AlGaN/undoped-AlGaN stack structure through a doping-selective electrochemical etching process. The reflectivity of the porous AlGaN reflector was 93% at 374u2009nm with a stop-bandwidth of 35u2009nm. In an angle-dependent reflectance measurement, the central wavelength of the porous AlGaN reflector had blueshift phenomenon by increasing light-incident angle from 10° to 50°. A cut-off wavelength was observed at 349u2009nm due to the material absorption of the porous-AlGaN/u-AlGaN stack structure. In the treated UV-LED structure, the photoluminescence emission wavelength was measured at 362u2009nm with a 106° divergent angle covered by the porous-AlGaN reflector. The light output power of the treated UV-LED structure was higher than that of the non-treated UV-LED structure due to the high light reflectance on the embedded porous AlGaN reflector.

Enhanced lithium-ion intercalation and conduction of transparent tantalum oxide films by lithium addition with an atmospheric pressure plasma jet

An investigation is conducted on enhancing lithium-ion intercalation and conduction performance of transparent organo tantalum oxide (TaOyCz) films, by addition of lithium via a fast co-synthesis onto 40xa0Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates at the short exposed durations of 33–34xa0s, using an atmospheric pressure plasma jet (APPJ) at various mixed concentrations of tantalum ethoxide [Ta(OC2H5)5] and lithium tert-butoxide [(CH3)3COLi] precursors. Transparent organo-lithiated tantalum oxide (LixTaOyCz) films expose noteworthy Li+ ion intercalation and conduction performance for 200 cycles of reversible Li+ ion intercalation and deintercalation in a 1xa0M LiClO4-propylene carbonate electrolyte, by switching measurements with a potential sweep from −1.25 to 1.25xa0V at a scan rate of 50xa0mV/s and a potential step at −1.25 and 1.25xa0V, even after being bent 360° around a 2.5-cm diameter rod for 1000 cycles. The Li+ ionic diffusion coefficient and conductivity of 6.2u2009×u200910−10xa0cm2/s and 6.0u2009×u200910−11xa0S/cm for TaOyCz films are greatly progressed of up to 9.6u2009×u200910−10xa0cm2/s and 7.8u2009×u200910−9xa0S/cm for LixTaOyCz films by co-synthesis with an APPJ.

Antibacterial capability of ZnO-based nanostructures manipulated by flake-coated onto silver wires

ZnO nanoscale structures were grown on the silver wire, utilizing the electro-hydrothermal method, which deposited to further grow flake-form with pellicle and floccule status via employing certain characterizations. The analysis reveals that ZnO nanoscale flake-form were successfully coated on Ag wire. Besides, the antibacterial testing of sample with ZnO nanoscale flake-form integrated on the polished silver wire may support future detection platforms.