Abstract: A method of forming a bipolar transistor with a vertical collector contact requires providing a transistor comprising a plurality of epitaxial semiconductor layers on a first substrate, and providing a host substrate. A metal collector contact is patterned on the top surface of the host substrate, and the plurality of epitaxial semiconductor layers is transferred from the first substrate onto the metal collector contact on the host substrate. The first substrate is suitably the growth substrate for the plurality of epitaxial semiconductor layers. The host substrate preferably has a higher thermal conductivity than does the first substrate, which improves the heat dissipation characteristics of the transistor and allows it to operate at higher power densities. A plurality of transistors may be transferred onto a common host substrate to form a multi-finger transistor.

Abstract: A method of forming an optical bridge waveguide between an optical element and an optical waveguide layer fabricated on a substrate such as a PIC platform. An optical element is heterogeneously integrated on the substrate. A first dielectric layer is deposited on the substrate and etched to a predetermined height. A second dielectric layer having a higher k than the first dielectric layer is deposited on the first dielectric layer, and a third dielectric layer having a lower k than the second dielectric layer is deposited on the second dielectric layer. The dielectric layers are formed such that the second dielectric layer provides an optical bridge waveguide between the optical element and optical waveguide layer, with the first and third dielectric layers providing a lower and upper cladding, respectively, for the optical bridge waveguide.

Abstract: A method of forming a bipolar transistor with a vertical collector contact requires providing a transistor comprising a plurality of epitaxial semiconductor layers on a first substrate, and providing a host substrate. A metal collector contact is patterned on the top surface of the host substrate, and the plurality of epitaxial semiconductor layers is transferred from the first substrate onto the metal collector contact on the host substrate. The first substrate is suitably the growth substrate for the plurality of epitaxial semiconductor layers. The host substrate preferably has a higher thermal conductivity than does the first substrate, which improves the heat dissipation characteristics of the transistor and allows it to operate at higher power densities. A plurality of transistors may be transferred onto a common host substrate to form a multi-finger transistor.

Abstract: A FET with a buried gate structure. The FET's gate electrode comprises a plurality of buried gate structures, the tops of which extend above the substrate's top surface and the bottoms of which are buried to a depth at least equal to that of the bottom of the channel layer, or the 2DEG plane within a channel layer for a HEMT, such that the buried gate structures contact the channel layer only from its sides. A head portion above and not in contact with the substrate's top surface contacts the tops of and interconnects all of the buried gate structures. Drain current is controlled by channel width modulation by lateral gating of the channel layer by the buried gates structures. The FET may include at least one field plate which comprises a slit structure in which the field plate is divided into segments.

Abstract: A FET with a buried gate structure. The FET's gate electrode comprises a plurality of buried gate structures, the tops of which extend above the substrate's top surface and the bottoms of which are buried to a depth at least equal to that of the bottom of the channel layer, or the 2DEG plane within a channel layer for a HEMT, such that the buried gate structures contact the channel layer only from its sides. A head portion above and not in contact with the substrate's top surface contacts the tops of and interconnects all of the buried gate structures. Drain current is controlled by channel width modulation by lateral gating of the channel layer by the buried gates structures. The FET may include at least one field plate which comprises a slit structure in which the field plate is divided into segments.

Abstract: Rapid temperature rises which characterize carbohydrate-nitric acid oxidation reactions used to form carbohydrate-derived acids may be moderated and temperature control readily maintained by blowing a gas such as air, oxygen, nitrogen or the like into the reaction mixture as needed to control the temperature of the reaction. The more moderate reaction conditions afford higher yield of the desired product with a concomitant reduction of byproducts which may be difficult to remove and usually are unwanted as well. Upon completion the oxidation mixture is made basic (e.g. with an alkali metal base hydroxide or carbonate, ammonia or an amine) to a pH at which the the carboxyl group or groups of the product carbohydrate-derived acid are entirely in the salt form. The aqueous solution is then passed through an ion retardation resin column to recover the carbohydrate-derived salt, using water as the eluent.