A method for fabricating Ag coated beam splitter is reported. This is showing specific patterned transmittance by
immersing glass substrates in the mixture of H<sub>2</sub>SO<sub>4</sub> and H<sub>2</sub>O<sub>2</sub> to make negatively charged oxygen sites at silica surface
and then in ethanolic solutions of AgNO<sub>3</sub> and butylamine. We controlled the soaking time and molar ratios of the
mixture of AgNO<sub>3</sub> and butylamine to pattern % transmittance of electroless coated glass surface. Finally, we made a
functionalized beam splitters showing step function like transmittance and applied this to make multiple laser beams for
display and laser machining.
Photonic device structures often require nano scale lithography techniques for their device fabrication. The techniques
are electron beam lithography and FIB(focused ion beam) pattering. Focused ion beam etching has been used as a
nanolithography tool for the creation of these nanostructures without mask. We obtain nano scale mesa patterns on
InGaN/GaN LED(light emitting diodes) wafer using focused ion beam and characterized. The InGaN/GaN LED wafer
was grown by molecular organic vapor deposition (MOCVD). To reduce the surface damage during FIB patterning, we
used a dielectric mask layer and wet etching to eliminate re-deposition of sputtering materials and Ga+ ion implantations
and ion damage layer during FIB patterning, and finally, removed SiO<sub>2</sub> with wet etching. A metal thin layer was
deposited by an ion beam sputter to avoid charging effects during FIB patterning. We obtain a 2-Dimensional patterning
for the fabrication of the high brightness LEDs. This FIB pattering technique can be applied to nanofabrication
We report new type of micro-EL instrument and its applications for light emitting devices. Our new micro-EL, so-called confocal scanning electroluminescence sprctro-microscope (CSESM) has not only fast image acquisition time but also high image resolution. The newly developed CSESM is combined with confocal laser scanning photoluminescence micsoscope, i.e. micro-PL. Therefore, micro-EL distribution can be directly matched with micro-PL and mechanical chip structure of LED. It is fruitful for providing a fast and non-destructive method to analyze the homogeneity of LEDs in its completely proceeded form. Using this apparatus, we study local intensity and wavelength distribution of electroluminescence for InGaN/GaN blue LED chip. Our results represent that local fluctuations of electroluminescence intensity and wavelength position are closely connected with the fluctuation of local current density, i.e. current spreading features on LED chips.
We present a converged spectroscopic system design for performing photoreflectance (PR), electroreflectance (ER), electroluminescence (EL), photoluminescence (PL) and photovoltage (PV) measurements of semiconductors. The design of the experimental setup is described in detail. To test the performance of the system, measurements of a series of In<sub>x</sub>Ga<sub>1-x</sub>N/GaN light emitting semiconductor with different indium composition of InGaN layer are carried out by use of this system. The experimental reflection and luminescence spectra are analyzed and discussed. The experimental results demonstrate the performance of this system. Optical and electrical properties of In<sub>0.15G</sub>a<sub>0.85</sub>N/GaN multi-quantum well (MQW) light-emitting diodes (LEDs) with different quantum well (QW) thicknesses were investigated by electric-field dependent ER spectroscopy. From the ER measurements, we have observed the well-resolved transition peaks related to InGaN QW. Furthermore, the
transitions related to yellow luminescence (YL) from Si-doped GaN and blue luminescence (BL) from Mg-doped GaN were observed in the ER spectra of In<sub>0.15</sub>Ga<sub>0.85N</sub>/GaN MQW LEDs. With increasing QW thickness, the additional transitions related to InGaN QW can be attributed to the recombination of excitons localized at the shallow potential states in InGaN QW, originating from the In-poor InGaN regions caused by indium phase
separation in InGaN QW. By applying a reverse bias voltage, the ER features related to InGaN QW were shifted
to higher energy, resulting from the reduction of quantum confined Stark effect in InGaN QW with increasing reverse bias voltage. On the other hand, the ER features from YL and BL band related to the deep and the shallow impurity state exhibit redshift and broaden with reverse bias voltage. These results can be attributed to the reduction of Coulomb interaction between donor and acceptor caused by the increase of depletion regions with increasing reverse bias voltage.
Excitonic carrier dynamics taking place in In<sub>x</sub>Ga<sub>1-x</sub>N/GaN multi-quantum-well systems have been studied by low temperature picosecond time resolved photoluminescence (LT-TRPL), HR-TEM, XPS, Dynamic TOF-SIMS, and quantum mechanical simulation methods. Both time-integrated and time-resolved photoluminescence spectra of In<sub>x</sub>Ga<sub>1-x</sub>N/GaN multi-quantum-wells with different well thickness and Indium composition were measured at 10 K. We assigned the natural radiative lifetime of each sample from the time resolved PL. We observed that the natural radiative lifetime of In In<sub>x</sub>Ga<sub>1-x</sub>N/GaN multi-quantum-wells depends strongly on the well thickness and Indium composition. To support the measured natural radiative lifetimes, excitonic oscillator strengths of the In<sub>x</sub>Ga<sub>1-x</sub>N/GaN multi-quantumwells were calculated by using a 2-D particle-in-a-box model as functions of well thickness and Indium composition. Values of the well thickness and Indium compositions from the HR-TEM and XPS compositional depth profiling were used to achieve more realistic computational results and to corroborate the measured natural radiative lifetimes of In<sub>x</sub>Ga<sub>1-x</sub>N/GaN multi-quantum wells.