Hsu-Yu Chang

Wavelength selective quantum dot infrared photodetector with periodic metal hole arrays

In this letter, the effect of extraordinary transmission of periodic metal hole arrays is directly integrated into the quantum dot infrared photodetector with broadband response. It is found that the detector response is strongly modulated by the extraordinary transmission from the excitation of surface plasmon.

Dispersion of surface plasmon polaritons on silver film with rectangular hole arrays in a square lattice

Extraordinary optical transmission through a two-dimensional Ag film in the far infrared region was demonstrated. The holes were rectangular and arranged in a square lattice. When either the width or the length size of the rectangular holes was close to the half of the lattice constant a∕2, the degenerate (±1,0) Ag∕Si or (0,±1) Ag∕Si modes split into two peaks. Additionally, the surface plasmon dispersion relations of the square hole array with different aspect ratios of holes were measured. As the aspect ratio increased, the surface plasmon tended to couple strongly with the local charge dipole oscillations in a direction perpendicular to the long edges. The charge dipole oscillation parallel to the long edges gradually disappeared. This is confirmed by experiments using the polarized light. The dynamic properties of the surface plasmon dispersion relations show the interaction among localized surface plasmons and its mechanism.

Bragg scattering of surface plasmon polaritons on extraordinary transmission through silver periodic perforated hole arrays

Extraordinary optical transmission through a two-dimensional periodic perforated Ag film in the far infrared region was demonstrated. When the squared hole size is close to a half lattice constant a∕2, the split of the degenerate (±1,0) Ag∕Si and (0,±1) Ag∕Si modes into two peaks becomes apparent. Surface plasmon polaritons dispersion relations with variously sized square holes are measured to investigate the different surface charge fields at the periodic metal array. Strong scattering of the forward SPP waves, in the (1,0) Ag∕Si mode, leads to a much lower transmission than that of in the (−1,0) Ag∕Si mode. Experimental results demonstrate that the photonic band gap opens up when the size of the squared hole exceeds a half lattice constant a∕2.

Energy-recycling pixel for active-matrix organic light-emitting diode display

The authors report a pixel structure for active-matrix organic light-emitting diode (OLED) displays that has a hydrogenated amorphous silicon solar cell inserted between the driving polycrystalline Si thin-film transistor and the pixel OLED. Such an active-matrix OLED pixel structure not only exhibits a reduced reflection (and thus improved contrast) compared to conventional OLEDs but also is capable of recycling both incident photon energies and internally generated OLED radiation. Such a feature of energy recycling may be of use for portable/mobile electronics, which are particularly power aware.

The low-temperature a-SiNx films with high impermeability and high optical gap with application to organic light-emitting diode

A low-temperature passivation layer (≦100°C) with high impermeability and a high optical gap is required in top-emitting organic light-emitting diodes. Hydrogenated amorphous silicon nitride (a-SiNx:H) films fabricated by the plasma-enhanced chemical-vapor deposition of SiH4+NH3+N2 at 100°C fulfill this requirement. Infrared-absorption spectroscopy was used to monitor the permeability of the a-SiNx:H film. The optimum a-SiNx:H film with an optical gap of 3.1eV was fabricated at a gas ratio of SiH4:NH3:N2=10:3:197SCCM. The main absorption peaks of the a-SiNx:H films deposited at 70°C did not change at all, even following a 3000-h-long storage test.

Coupling between surface plasmons via thermal emission of a dielectric layer sandwiched between two metal periodic layers

Metal/SiO2/metal trilayer thermally generated infrared emitters with different top and bottom periodic metal arrangements were fabricated and their emission spectra were measured. The coupling mechanisms of surface plasmon polaritons at top and bottom periodic metal structures were characterized. It is found that the top surface plasmon converted to light radiation directly, whereas the bottom surface plasmon can radiate out when its emission peak position matches that of the top surface plasmon. This opens the way to fabricate the high temperature operated, narrow bandwidth, and multiwavelength infrared light source.

Low Temperature Polycrystalline Silicon TFTs on Polyimide and Glass Substrates

This paper presents results on low temperature poly-silicon thin film transistors (TFTs) prepared by KrF excimer laser annealing of hydrogenated amorphous silicon (a-Si:H) on polyimide and glass substrate. Two step laser annealing is used in dehydrogenation and crystallization of the a-Si:H into poly-Si on polyimide substrate. From the Raman spectrum, it is found that the crystallinity of the poly-Si on the polyimide substrate is better than that on the glass. The fabricated poly-Si TFT on polyimide shows a very good performance with field effect mobility of 370 cm2/V-sec and on/off current ratio > 106.

The Improvement of Polycrystalline Silicon TFTs Fabricated by Employing Periodic Metal Pads

Polysilicon films with regular-sized and large grains were fabricated by employing periodic metal (Cr-Al) pads as the heat sinks and with underlying silicon oxynitride (SiON) as the heat absorption layer. The poly-Si could grow to regular hexagonal grains after excimer laser annealing (ELA). The thin-film transistors (TFTs) fabricated by this method show uniform characteristics that are suitable for large-area applications. The TFT achieves a field-effect mobility of 270 cm2/Vmiddots and an on-off current ratio exceeding 108 . It is found that the TFT with the smaller channel width and length results in a better subthreshold swing because it contains fewer grain boundaries and, thus, fewer defects. After comparing the performance of TFTs using either double-metal Cr-Al or single-metal Al photonic-crystal pads, it is found that the Cr could efficiently impede the diffusion of Al into Si during ELA

Uniform Square Polycrystalline Silicon Fabricated by Employing Periodic Metallic Pads and SiON Absorption Layer for Thin Film Transistors

The poly crystalline silicon with regular square grains is fabricated by employing metallic (Cr/Al) periodic pads as the heat sinks and with underlying silicon oxynitride (SiON) as the heat absorption layer. The maximum lateral growth length of the poly-Si is 1.78 mum by this method. If the metal pads are periodically arranged, the poly-Si can grow to regular square grains following the high power excimer laser annealing. After removing the metallic pads, the low power laser shot transfers the a-Si:H under the original metallic pads to poly-Si without destroying the square grains. The TFTs fabricated by this method achieve a field effect mobility of 450 cm2/Vmiddots and an on/off current ratio exceeding 107. It is found that the TFT with smaller channel width and length results in a better subthreshold swing because it contains fewer grain boundaries and defects.