Effects of peripheral-surface damages on breakdown characteristics of n^{++}-n-n^{+} epitaxial GaAs bulk diodes were investigated experimentally. Critical voltages for switching from a high-voltage saturating-current state to a high-current low-voltage state were measured on a number of mechanically diced cubic-type elements and on chemically etched mesa-type elements. It was found that the switching voltages of the mesa-type diodes were much higher and more uniform than those of the cubic type. The difference in the switching voltages between the two types is ascribed to the peripheral-surface damages produced on the cubic-type elements during wire saw cutting. It was concluded that the elimination of the peripheral surface damages is important to obtain GaAs bulk diodes of high reliability.
In order to realize practical GaAs bulk effect functional devices, it is necessary as a first step to demonstrate actually the capability of CW Gunn oscillation in planar-type diodes. This paper describes the results of CW oscillations obtained in GaAs planar-type bulk diodes. The n-type layer grown by vapor process on a Cr-doped semi-insulating substrate has 0.4-2 × 1015cm-3carriers and is 10-35µ thick. Effective electrode spacing ranges 50-200µ. The most important things in obtaining reliable CW oscillations are the quality and geometry of the electrode-contacts as well as GaAs crystals of sufficient homogeneity. CW oscillations with satisfactory reliability have been obtained by adopting I and T shaped geometry for the n-type layer. The low-field resistance of the device is of the order of about 1kΩ. Fundamental oscillation frequencies of 0.5-3 GHz have been observed. The device construction and fabrication techniques as well as microwave oscillation characteristics such as output power, efficiency, etc., will be presented in detail.
We present an ultra-high-performance 0.13-/spl mu/m embedded DRAM technology, which improves transistor performance in both logic devices and DRAM cells. Simulation results indicate that the typical random access cycle of a 16-Mbit DRAM core exceeds 570 MHz. The full-metal DRAM structure having a newly developed TiN/HfO/sub 2//TiN/W capacitor minimizes the aspect ratio of the cylindrical capacitor electrode to reduce contact resistance in the logic area. Integration of the embedded DRAM with BSTSOI (Body-Slightly-Tied SOI) is also demonstrated, with which the logic performance can be further improved and the DRAM cell area is free from floating-body effects.
A three-terminal bulk-effect pulse regenerator that is operable under dc bias has been successfully obtained. The device can generate a rectangular pulse of 0.3-1 ns in width with output power levels of 0.5-1.2 V into a 50-Ω line. Minimum input signal required is about 0.2-0.4 V.
Anti-reflection characteristics in one dimensional tapered (grating) structures with different pitches which have been fabricated by femtosecond laser processing, have been evaluated experimentally and theoretically at terahertz frequencies. The measured reflectance depending on the frequency in the grating structures have been good agreement with theoretical ones. The results have shown that the laser processing is useful to fabricate anti-reflection structures with precise dimensions.
Terahertz antireflective structures on Si substrates are fabricated by femtosecond laser processing. The structure is constituted by periodic grooves at micro order. Their antireflective characteristics are evaluated by THz-TDS (terahertz time-domain spectroscopy). The results show that the surface reflectance is almost decreased to 0 and antireflection band was widened by improving aspect ratio of grooves.
Anti-reflective structures formed by periodic grooves, have been fabricated by femtosecond laser processing. Molten materials due to thermal influence during processing hindered the obtaining of high aspect ratio (=depth/pitch in tapers) and shape control of the taper. These are important to improve the anti-reflective characteristics of these structures. By increasing the scan speed of laser beam, we decreased the effective pulse number to reduce the thermal influence. By controlling the pitch of these tapers, we fabricated tapered structures with different anti-reflective band.
A high-speed three-terminal pulse regenerator that is operable under dc-biased conditions and having the trigger sensitivity of as small as 0.1 volt has been developed to a practical level for the first time. The device can generate pulses of 0.3 - 1 ns width with output power levels in excess of 0.5 volt into a 50 Ω line.
