Yoshiteru Shimizu

High-speed low-loss p-n diode having a channel structure

A p-n diode having a channel structure (static shielding diode, SSD) is proposed to increase the reverse blocking voltage of a low-loss high-speed p-n diode. It is shown by numerical analysis and experiment that a low-loss, high-speed SSD with high blocking capability can be realized by surrounding the p-layer and a portion of the n-layer with a highly doped p+-layer. In this method, the blocking voltage can be increased by a factor of 2 to 3.5 without sacrificing the low forward voltage drop and fast reverse recovery. The SSD with a 0.81-V forward voltage drop at 80 A/cm2, a 180-V blocking voltage at 150°C, and a 87-ns reverse recovery time can be fabricated.

32.2: An Innovative Pixel-Driving Scheme for 64-Level Gray-Scale Full-Color Active Matrix OLED Displays

Innovative pixel driving for active matrix OLED displays is described. A full-color display with a luminous deviation of less than 1.6%, which means a 6-bit or 64-level gray-scale accuracy, is shown. The driving is preferable for full-color video with gamma correction.

A high performance intelligent IGBT with overcurrent protection

We have proposed a 600 V, 30 A IGBT, having a novel overcurrent protection circuit, on one chip. The protection circuit was fabricated on a silicon wafer coated with a polycrystalline silicon film. A Zener diode was used in the gate suppress circuit to keep the gate voltage at the controlled value. An overcurrent limitation function was successfully obtained with no oscillation. The fabricated device has an on-state voltage of 1.50 V at 100 A/cm/sup 2/. The turn-off fall time is 0.28 /spl mu/s. This trade-off value is almost at the limit of this class of planer-gate IGBT.

51.1: A 2.5‐inch OLED Display with a Three‐TFT Pixel Circuit for Clamped Inverter Driving

A new pixel circuit for “clamped inverter driving” was developed. Since a PMOS inverter is applied instead of the conventional CMOS for the pixel circuit, the circuit is simplified and is composed of only three TFTs. A simulation of gray-scale characteristics verified that this pixel circuit can compensate variation in Vth and carrier mobility. A 2.5-inch OLED display based on the new pixel circuit was fabricated by LTPS processing and achieves 6-bit gray-scale and good uniformity.

Numerical analysis of turn-off characteristics for a gate turn-off thyristor with a shorted anode emitter

Turn-off current waveform for a gate turn-off thyristor (GTO) with a shorted anode emitter has been calculated numerically by solving the semiconductor basic equations in an equivalent one-dimensional model device. This model is derived from the analysis of current and carrier distributions obtained by a two-dimensional calculation of the on-state of GTO. A calculated turn-off current waveform agrees well with the experimental waveform. The computational time of one case is about 2 min. It is shown that this one-dimensional analysis method is useful for the calculation of the turn-off time. Using this one-dimensional model during the turn-off process and the two-dimensional model in the on-state, the relation between turn-off time and the forward voltage drop can be obtained in relation to the shorted emitter structure. It is shown that the shorted emitter structure is useful to improve this tradeoff relation.

A study on maximum turn-off current of a high-power GTO

A 6 kV, 6 kA pnpn-type GTO was fabricated and its maximum turn-off current was investigated. The simulation uses a three-segment device model together with an equivalent circuit model. Results of simulations with segments having different on-state voltages showed current concentration in the lower on-state voltage segment in the fall period. By introducing a homogeneous fabrication process, the on-state voltage distribution band was decreased by a factor of 2. The circuit model simulation results showed the maximum peak current of the improved GTO with smaller on-state voltage band was reduced by a factor of 1.33 compared to that of the conventional GTO. A high-power GTO turn-off limiting model was proposed from the measured 6 kA GTO turn-off locus and the segment SOAs. This turn-off limiting model showed that the GTO would be destroyed when the segment current exceeds the SOA at the time a spike voltage occurs in the fall period. It was demonstrated that the maximum turn-off current estimated by this limiting model coincided well with the experimental results.

A high-voltage light-activated thyristor with a novel over-voltage self-protection structure

A new type of high voltage self-protected thyristor with a well structure formed in its p-base layer is described. The device structure is simple and easy to fabricate compared to past devices. Numerical analyses and experiments demonstrate that the breakover voltage of this thyristor can be controlled by varying the well diameter and its depth. The breakdown voltage fluctuation of the device is 10% when the junction temperature is varied from 23°C to 100°C. This device is turned on safely at 7300 V. Fabricated devices show no degrading in important thyristor features.

49.4: Two TFT Pixel Circuit with Non-Uniformity Suppress-Function for Voltage Programming Active Matrix OLED Displays

We proposed the worlds first two TFT pixel circuit with an inter-pixel non-uniformity suppress-function for the analog voltage programming to assist in the realization of small pixel bottom emission OLED displays. The pixel circuit provides larger OLED fill factor. We fabricated a 2.5 inch 240 (V) × 960 (H) pixel monochrome bottom emission display.

High power GTO with high turn-off ruggedness

A 6 kV, 6 kA pnpn type GTO was fabricated and its turn-off failure mechanism was investigated. Current concentration progressed remarkably in the fall period according to a simulation model. The homogenizing GTO segment on-state voltage was effective for reducing the current concentration. The maximum controllable current was increased by a factor of 1.2 by introducing a homogeneity fabrication process.

An overvoltage self-protected thyristor with a structure to predict breakover voltage

A new concept for an overvoltage self-protected thyristor was theoretically analyzed and the thyristor manufactured. Its breakover operation is basically a combination of punchthrough and avalanche phenomena. Temperature dependence of the original structure in this thyristor is 5% from 20 to 125/spl deg/C. A second device which has a function to predict breakover voltage was also produced. The difference in temperature dependence of breakover voltage for both devices was investigated by an analytical model. Structures offering improved characteristics were proposed. The breakover voltage decrease of the developed structures at high temperature could be made equal to that of the original structure by a slight modification of the breakover region.