Katsuyoshi Fukuda

SAW Propagation Characteristics on Li2B4O7

Lithium tetraborate (Li2B4O7) was reported as a new piezoelectric material which has zero temperature coefficient of delay (TCD) and moderately high coupling coefficient (k2). This paper estimates SAW propagation properties (k2 and TCD) on Li2B4O7 over the full cuts and propagation directions. Further, the TCD dependency on aluminum layer is also assessed, considering construction of a SAW device with aluminum electrodes. As a result, it is found that there is a region of zero TCD and high coupling coefficient (1%).

Highly Integrated Field Emitter Arrays Fabricated by Transfer Mold Technique

Highly integrated field emitter arrays (FEAs) have been fabricated by the transfer mold technique to obtain highly uniform and stable field emission for highly efficient and reliable vacuum microelectronic devices. Transfer mold Mo FEAs containing 9,400,000 emitter tips with high emitter density of 7,840,000 tips/cm2 have demonstrated a low value of less than 0.7%. Highly uniform, and flickerless fluorescence has been observed in the entire area of the fluorescent screen corresponding to the FEAs. The principle of the vacuum microelectronic switching devices has been proposed and experimentally verified by applying a high anode voltage of ±1 kV, which will be capable of decreasing the size and the electric power loss of the high voltage electric power converters using conventional semiconductor devices such as light-triggered thyristors (LTT) and gate turn off thyristors (GTO) to less than 1/100 and 1/10, respectively.

Scatterings of Shallow Threshold Voltage on Si-Implanted WN Self-Alignment Gate GaAs Metal-Semiconductor Field-Effect Transistors on Different Composition 2-Inch Substrates by Growing in Three Kinds of Furnaces

Two-inch undoped GaAs crystal boules were grown from different composition melts in a pyrolytic boron nitride crucible in three kinds of furnaces in order to survey composition effect through a consecutive thermal cooling cycle after crystallization on Vth scattering of Si-implanted metal-semiconductor field-effect transistors (MESFETs). On the substrates (dislocation density: 2×103-105 cm-2 order) obtained from the crystal boules, a tungsten nitride self-alignment gate MESFET array of shallow Vth (3×1012 cm-2, 50 keV) was fabricated, and Vth scatterings were observed on them. The Vth scattering for the most As-rich melt-grown crystal boule in the furnace with the smallest ratio of bottom heating was the smallest as compared with those for the slightly Ga-rich or As-rich melt-grown crystal boules in the furnaces with the greatest ratio of bottom heating. There was an anticorrelation between the Vth scattering amplitude and carbon content in the substrate crystals.

Channeling Phenomena of Direct Si-Implantation to Liquid-Glass Encapsulation Czochralski GaAs Crystal Wafers Through Observation of Threshold Voltages

Threshold voltages of Si-implanted gallium arsenide (GaAs) MESFETs depend on not only wafer crystallographic characteristics, but also MESFET fabrication processes. When the position of the orientation flat was changed to improve mechanical shock tolerance, it was found that Vth varied on the wafers due to a crystallographic orientation effect on the Si implantation. Thus, we investigated Vth distributions on wafers of several different Si implantation orientations. It was confirmed that Vth largely varies according to Si-implantation orientations.