Abstract: A high electron mobility transistor is disclosed which has a double-layered main semiconductor region formed on a silicon substrate via a multilayered buffer region. The multilayered buffer region is in the form of alternations of an aluminum nitride layer and a gallium nitride layer. The main semiconductor region, buffer region, and part of the substrate taper as they extend away from the rest of the substrate, providing slanting side surfaces. An electroconductive antileakage overlay covers these side surfaces via an electrically insulating overlay. Electrically coupled to the silicon substrate via a contact electrode, the antileakage overlay serves for reduction of current leakage along the side surfaces.

Abstract: A substrate system of the kind having a buffer region interposed between a silicon substrate proper and a nitride semiconductor region in order to make up for a difference in linear expansion coefficient therebetween. Electrodes are formed on the nitride semiconductor layer or layers in order to provide HEMTs or MESFETs. The buffer region is a lamination of a multiplicity of buffer layers each comprising a first, a second, and a third buffer sublayer of nitride semiconductors, in that order from the silicon substrate proper toward the nitride semiconductor region. The three sublayers of each buffer layer contain aluminum in varying proportions including zero. The aluminum proportion of the third buffer sublayer is either zero or intermediate that of the first buffer sublayer and that of the second.

Abstract: A printing hammer assembly for use in impact printers includes a printing hammer which has an impact surface and an armature and which is supported to be movable in a reciprocating manner along its longitudinal axis, a driving solenoid which drives to move the printing hammer forward when energized against the force of a coil spring which normally applies a biasing force to the printing hammer in the backward direction and a yoke leading a magnetic flux produced by said solenoid to the armature of printing hammer. A pair of magnets are disposed such that they are magnetically repulsive to each other with one of them fixed in position and the other movable over a predetermined distance thereby allowing to absorb the rebounding energy of the hammer when it returns to its home position.

Abstract: An aluminum-based die casting alloy for producing high strength, crack free die castings, comprising 4-8% Zn, 6-11% Mg, 0.05-0.45% Ti and/or Zr if desired, and the balance aluminum. In one embodiment, the die casting alloy may further comprise 0.3-2.0% Fe to prevent the die casting alloy in the molten state from eroding the gate and its neighborhood of a die during casting in the die.