Hydrogenated polymorphous Silicon allows to fabricate TFTs with very interesting characteristics including better threshold voltage stability than a-Si TFTs, lower leakage current than µc-Si:H TFTs and excellent uniformity. Investigation of threshold voltage shift mechanisms of pm-Si:H TFTs has shown a specific semiconductor material degradation with different activation energies compared to a-Si:H TFTs. TEM analysis has evidenced for the first time a significant structural difference between pm-Si:H and a-Si:H materials, in the TFT device configuration. Pm-Si:H appears to be very suitable for low cost and high performance AM-OLED fabrication.

A new pixel design and driving method for active matrix organic light emitting diode (AMOLED) displays that use low-temperature polycrystalline silicon thin-film transistors (LTPS-TFTs) with a voltage programming method are proposed and verified using the SPICE simulator. We had employed an appropriate TFT model in SPICE simulation to demonstrate the performance of the pixel circuit. The OLED anode voltage variation error rates are below 0.35% under driving TFT threshold voltage deviation (Δ Vth = 0.33 V). The OLED current non-uniformity caused by the OLED threshold voltage degradation (Δ VTO = +0.33 V) is significantly reduced (below 6%). The simulation results show that the pixel design can improve the display image non-uniformity by compensating for the threshold voltage deviation in the driving TFT and the OLED threshold voltage degradation at the same time.

We carried out degradation analysis of a blue phosphorescent organic light emitting diode by both impedance spectroscopy and transient electroluminescence (EL) spectroscopy. The number of semicircles observed in the Cole-Cole plot of the modulus became three to two after the device was operated for 567 hours. Considering the effective layer thickness of the initial and degraded devices did not change by degradation and combining the analysis of the Bode-plot of the imaginary part of the modulus, the relaxation times of emission layer and hole-blocking with electron transport layers changed to nearly the same value by the increase of the resistance of emission layer. Decay time of transient EL of the initial device was coincident with that of the degraded one. These phenomena suggest that no phosphorescence quenching sites are generated in the degraded device, but the number of the emission sites decrease by degradation.

We have fabricated the transparent bottom gate and top gate TFTs using new oxide material of Al-Zn-Sn-O (AZTO) as an active layer. The AZTO active layer was deposited by RF magnetron sputtering at room temperature. Our novel TFT showed good TFT performance without post-annealing. The field effect mobility and the sub-threshold swing were improved by the post-annealing, and the mobility increased with SnO2 content. The AZTO TFT (about 4 mol% AlOx, 66 mol% ZnO, and 30 mol% SnO2) exhibited a mobility of 10.3 cm2/Vs, a turn-on voltage of 0.4 V, a sub-threshold swing of 0.6 V/dec, and an on/off ratio of 109. Though the bottom gate AZTO TFT showed good electrical performance, the bias stability was relatively poor. The bias stability was significantly improved in the top gate AZTO TFT. We have successfully fabricated the transparent AMOLED panel using the back-plane composed with top gate AZTO TFT array.

We have developed a high-speed electroabsorption modulator integrated distributed feedback (EA/DFB) lasers. Transmission performance over 10 km was investigated under 25 Gbps and 43 Gbps modulation. In addition, the feasibility of wide temperature range operation was also investigated. An uncooled EA/DFB laser can contribute to the realization of low-power-consumption, small-footprint and cost-effective transceiver module. In this study, we used the temperature-tolerant InGaAlAs materials in an EA modulator. A wide temperature ranged 12 km transmission with over 9.6 dB dynamic extinction ratio was demonstrated under 25 Gbps modulation. A 43 Gbps 10 km transmission was also demonstrated. The laser achieved a clear, opened eye diagram with a dynamic extinction ratio over 7 dB from 25 to 85. The modulated output power was more than +2.9 dBm even at 85. These devices are suitable for next-generation, high-speed network systems, such as 40 Gbps and 100 Gbps Ethernet.

High-efficiency pure-white organic light-emitting diodes (OLEDs) were fabricated using small polysilicic acid nanodot embedded polymeric hole-transporting layer. By incorporating the nanodot, the efficiency of a solution-processed phosphorescent white OLED was increased from 6.8 to 23.7 lm/W, an improvement of 250%. 17.1 lm/W was obtained while the same concept was applied on a mixed-host composed fluorescent white OLED.

We developed a 44 SFQ network switch prototype system and demonstrated its operation at 10 Gbps. The system's core is composed of two SFQ chips: a 44 switch and a 6-channel voltage driver. The 44 switch chip contained both a switch fabric (i.e. a data path) and a switch scheduler (i.e. a controller). Both chips were attached to a multi-chip-module (MCM) carrier, which was then installed in a cryocooled system with 32 10-Gbps ports. Each chip contained about 2100 Josephson junctions on a 5-mm5-mm die. An NEC standard 2.5-kA/cm2 fabrication process was used for the switch chip. We increased the critical current density to 10 kA/cm2 for the driver chip to improve speed while maintaining wide bias margins. MCM implementation enabled us to use a hybrid critical current density technology. Voltage pulses were transferred between two chips through passive transmission lines on the MCM carrier. The cryocooled system was cooled down to about 4 K using a two-stage 1-W cryocooler. We correctly operated the whole system at 10 Gbps. The switch scheduler, which is driven by an on-chip clock generator, operated at 40 GHz. The speed gap between SFQ and room temperature devices was filled by on-chip SFQ FIFO buffers or shift registers. We measured the bit error rate at 10 Gbps and found that it was on the order of 10-13 for the 44 SFQ switch fabric. In addition, using semiconductor interface circuitry, we built a four-port SFQ Ethernet switch. All the components except for a compressor were installed in a standard 19-inch rack, filling a space 21 U (933.5 mm or 36.75 inches) in height. After four personal computers (PCs) were connected to the switch, we have successfully transferred video data between them.

A novel driving concept, "pulse-width modulation with current uniformization," is proposed for thin-film transistor driven organic light-emitting diode displays (TFT-OLEDs). An example of this driving concept is the combination of "pulse-width modulation with a self-biased inverter" and a "time-ratio grayscale with current uniformization." Its driving operation is confirmed by circuit simulation. It is found that this driving method can compensate the characteristic deviations and degradations of both TFTs and OLEDs and immensely improve luminance uniformity. Finally, its driving operation is also confirmed by an actual pixel equivalent circuit.

We present the 10-bit current driver LSI with 2-set current digital-to-analog converters (DACs) and output channel current sample and hold (S/H) circuits for large-size and high-resolution active matrix organic light emitting diode (AMOLED) display applications. This current driver LSI has 300 output channels and the output current ranges from 0 µA to 290 µA. The maximum output current level can be controlled by 2-bit control signals because the maximum output current level depends on display size and resolution. The chip was fabricated using 0.65µm BiCMOS process and characterized. The chip size is 16.8 mm3.6 mm. Experimental results show that the output current DNL is less than 0.4 LSB and that INL is less than 1.5 LSB. This is good enough to apply 15.5 inch WXGA (1280RGB768) AMOLED displays.

Driving methods for TFT-OLEDs are explained with their features and classified from the viewpoints of grayscale methods and uniformizing methods. This classification leads us to a novel proposal using time ratio grayscale and current uniformization. This driving method maintains current uniformity and simultaneously overcomes charging shortage of the pixel circuit for low grayscale levels and current variation due to the shift of operating points. Tolerance toward degraded characteristics, linearity of grayscale and luminance uniformity against degraded characteristics are confirmed using circuit simulation.

This paper describes 40-Gbit/s operation of 1.55-µm electro-absorption (EA) modulators applicable to compact and low-cost transmitters for very-short-reach (VSR) applications. We start by identifying factors that make a multi-quantum-well (MQW) design suitable for high levels of output power and for uncooled operation. From the basic experimental results, we determine that a valence-band discontinuity ΔEv at around 80 meV is optimal in terms of combining high-output-power operation and a good extinction ratio. We then apply the above findings in an InGaAsP-MQW EA modulator that is monolithically integrated with a distributed feedback (DFB) laser, and thus obtain operation with high output power (+1.2 dBm), a high ER (10.5 dB), and a low power penalty (0.4 dB after transmission over 2.6 km of single-mode-fiber). These results confirm the applicability of our EA modulator/DFB laser to VSR applications. After that, we theoretically demonstrate the superiority in terms of ER characteristics of the InGaAlAs-MQW over the conventional InGaAsP-MQW. InGaAlAs-MQW EA modulators are fabricated and demonstrate, for the first time, 40-Gbit/s operation over a wide temperature range (0 to 85).

Time resolved photoluminescence measurements of lanthanide and group III metal chelates of 8-hydroxyquinoline (Q) have been performed as a function of temperature and excitation wavelength. For the lanthanide complexes it has been shown that either singlet or triplet luminescence can be observed depending on the excitation wavelength. Lifetime measurements of these emissions show that competing non-radiative paths are very important in the performance of these molecules. For ErQ we have shown that it is the singlet state that couples most efficiently to the ion. Radiative lifetime measurements of the ion emission show relatively short lifetimes that are indicative of quenching mechanisms. For the group III metal chelates at room temperature the luminescence is dominated by the singlet emission but at 80 K there is evidence that triplet emission can occur when the molecule is excited at long wavelengths. Luminescence lifetime measurements of the emission from the lanthanide ions: erbium, neodymium and ytterbium all show effective lifetimes of the order of microseconds which is very fast compared to the lifetimes of the free ions. Using excitation directly into the lanthanide ion (e.g.980 nm excitation for erbium) and via the organic ligands (400 nm excitation) we have seen that there are no changes in the emission lifetimes and hence the exciton transfer from the ligand to the lanthanide ion is not a rate limiting step.

Thin film of polyurethane having metal complex was prepared by vapor deposition polymerization of bis (5,8-dihydroxyquinoline) zinc (ZnHq2) and 4, 4'-diphenylmethane diisocyanate monomers. The film was applied for the electron-transporting emissive layer of the organic light emitting diode. The deposition-polymerized film was found to give higher quantum efficiency of luminescence than the ZnHq2 monomer film.

We fabricate the organic light-emitting devices (OLEDs), which have dot array structures with organic layer, and discuss the improvement of coupling-out efficiency.

We have developed a 17-inch WXGA full-color polymer OLED display by using newly developed ink-jet printing method. On the ink-jet technology, both droplet volume and landing position were precisely controlled pixel by pixel in order to get luminance uniformity. A pixel circuit having Vth variation-cancellation was adopted and the circuit was modified to realize high uniformity and high gray scale reproduction under the short horizontal period operation. Correction on gamma profile difference among RGB OLEDs was achieved by optimizing on configuration between integrated source driver circuit and outer reference voltage circuit in spite of using a common source driver IC having only one gamma profile. Peak control system, that is important for the large size and high luminance display, was utilized and improved image quality on human feeling and actual power consumption. With these efforts a uniform picture with 260,000 colors and wide viewing angle was achieved. It was proved that the ink-jet method was the optimal manufacturing technology for large-size and high-resolution OLED displays. And we found there is no singular problem on the large size OLED display utilized the ink-jet technology.

In this letter, we propose new driving methods for designing a driver independent of the current property of Organic Light Emitting Diodes (OLED) displays. The proposed methods are the Look-Up Table (LUT) and the Pulse Width Modulation (PWM). The LUT is used to handle the amount of the current for driving the OLED display panel and the PWM is applied to represent the gray scale on the OLED display panel. In particular, the proposed methods are used for the manufacturing of 1.8" 128 128 dot passive matrix OLED display panel. The designed circuit was fabricated using 0.6 µm, 2-poly, 3-metal CMOS process and applied to the Personal Communication System (PCS) phone successfully.

We proposed the conduction mechanism of organic light-emitting diode (OLED) using a one-dimensional discontinuous model. We assumed that each emitting molecule corresponds to a hopping site according to the actual charge transfer between adjacent molecules. Both carrier mobility of Alq3 and barrier heights for each carrier were derived from experimental data. We calculate transient behavior of carrier, field, and exciton distribution. Both carrier injections assumed the Schottky injection. In the previous results, when we assumed that calculated current density fit the experimental one in the current density field curve, calculated light-emission intensity did not fit the experimental one in the light-emission field curve. Furthermore, the slope of the calculated light emission-field curve is too small to fit the experimental one. In the previous study, hopping distance was assumed to be 1 nm. In this study, it is assumed to be 1.7 nm. We consider that field dependence of electron injection is too weak to explain only the Schottky emission. When the electron injection is assumed to be both Schottky emission and Fowler-Nordheim emission calculated light-emission field as well as the current-density field curves were fit to the curve of each experimental characteristics.

Organic light emitting diodes (OLEDs) containing nanostructured cathode buffer layers were fabricated, and their electrical and emitting properties were investigated. The OLEDs have an ITO anode/CuPc/TPD/Alq3/buffer layer/Al cathode structure with the buffer layers made from nanostructured alternating layers Alq3 and Al. The driving voltage and the efficiency of the devices were improved by insertion of the buffer layer. It was estimated that some modulations of the Schottky barrier at the Alq3 and the Al cathode interface were induced due to the insertion of the buffer layer and it caused an enhancement of electron injection from the Al cathode.

In this paper, we propose a fine grain Cooled Logic architecture for low-power oriented processors. Cooled Logic detects, in novel hardware method with dual-rail logic, functional blocks to be active, and stops clocks to each of the functional blocks in order to make it inactive at certain periods. To confirm the effectiveness of our approach, we design a 4-bit and a 16-bit event-driven array multipliers, and analyze their power consumption by the HSPICE simulator. As a result, it is shown that Cooled Logic has a tendency to reduce power consumptions in both the functional blocks and the clock drivers of the multipliers.

In this study, we prepared red organic light- emitting-diode (OLED) with a fluorescent dye(Sq)-doped and inserted 1,3-bis (5-p-t-butylphenyl)-1,3,4-oxadiazol-2-yl) benzene (OXD7) or/and tris (8-hydroxyquinoline) aluminum (Alq3) layers between emission layer and cathode in order to increase electroluminescent (EL) efficiency. This inserting effect has been observed and EL mechanism characteristics have been examined. The hole transport layer was N,N'-diphenyl-N, N'bis-(3-methylphenyl)-1,1'diphenyl-4,4'-diamine (TPD); the host material of emission layer was Alq3; the guest material of emission layer was Sq. When Alq3 was inserted between the emission layer and the cathode, emission efficiency increased. Highly pure red emission, however, was not attaina ble with Alq3. On the other hand, the insertion of OXD7 between the two layers blocked and accumulated holes. Because of its increasing recombination probability of electron and hole, luminance characteristics and emission efficiency were improved with holding highly pure red color.