Hughes Aircraft Company

University of California

James D Parsons

Oscar Magnus Stafsudd

Rointan F Bunshah

David E Snyder

Alfred S Yue

Duncan W Brown

Lawrence S Lichtmann

A new type of semiconductor material is disclosed which consists of a .beta.-SiC:metal carbide alloy having the general formula Si.sub.w (metal 1).sub.x (metal 2).sub.y (metal 3).sub.z C, where w+x+y+z=1 and 1&gt;w&gt;0. The metals are selected from the group consisting of Ti, Hf, Zr, V, Ta, Mo, W and Nb, with Ti, Hf, and Zr preferred. By selecting appropriate proportions of metal carbide and SiC, the alloy's bandgap may be tailored to any desired level between the bandgaps of the metal carbide and SiC. Semiconductor devices are preferably formed by epitaxially growing a layer of the new alloy upon a substrate having a .beta.-SiC or TiC type crystal structure. In addition to retaining the benefits of single-bandgap .beta.-SiC with certain advantages, the new alloys make it possible to implement various electrical devices that cannot be achieved with .beta.-SiC, and also have a potential for bandfolded superlattices for infrared detectors and lasers.

Silicon carbide:metal carbide alloy semiconductor and method of making

A semiconductor device wafer base wherein devices may be fabricated in silicon carbide, the base having a compatible substrate and a beta silicon carbide overlay layer epitaxially related to the substrate, the beta silicon carbide layer being unpolytyped, single crystal, uncracked, without twins, and having integrated circuit quality surface morphology. Preferably, the substrate is a single crystal of titanium carbide, which is the same cubic lattice-type as beta silicon carbide with a lattice parameter different from that of beta silicon carbide by less than about 1%. Additionally, the thermal expansion coefficients of beta silicon carbide and titanium carbide are nearly the same, minimizing the creation of thermal stresses during cooling and heating. The beta silicon carbide is useful in fabricating semi-conductor devices for use at much higher temperatures than is silicon, and for use at high power levels, at high frequencies, and in radiation hardened applications. The device base may be fabricated by any suitable technique, including reactive deposition and chemical vapor deposition.

Wafer base for silicon carbide semiconductor device

Silicon carbide is deposted by chemical vapor deposition from a vapor source having a single molecular species that provides both the silicon and the carbon. The molecular species has the composition C.sub.n Si.sub.n H.sub.m, where m ranges from 2n+1 to 4n+1 inclusive and n ranges from 2 to 6 inclusive, and exhibits a primary pyrolysis mechanism producing reactive fragments containing both silicon and carbon atoms. Unbalanced decomposition paths are avoided. The silicon and carbon atoms are necessarily codeposited in equal numbers and at equal rates onto the substrate, producing stoichiometric deposited silicon carbide. Preferred molecular sources include H.sub.3 SiCH.sub.2 CH.sub.2 SiH.sub.3, a silacycloalkane of the form (--SiH.sub.2 CH.sub.2 --).sub.p, where p is 2, 3, 4, or 5, and a cyclic structure of the form (--SiH(CH.sub.3)--).sub.q, where q is 4 or 5.

Chemical vapor desposition of silicon carbide

A method for chemical vapor deposition of materials containing tellurium, such as cadmium telluride and mercury cadmium telluride, wherein the reactant source of the tellurium is a tellurophene or methyltellurol. These reactant sources have high vapor pressures, and the reactant source vapors emitted from the reactant sources have decomposition temperatures of less than about 300.degree. C., so that deposition may be accomplished at low temperatures of about 250.degree. C. The reactant source vapor containing tellurium is mixed with a reactant source vapor containing another substance to be codeposited, such as dimethylcadmium or dimethylmercury, and contacted with a substrate maintained at the deposition temperature, the deposition being preferably accomplished in an inverted vertical chemical vapor deposition reactor.

Method for depositing materials containing tellurium and product

A semiconductor device wafer base wherein devices may be fabricated in silicon carbide, the base having a compatible substrate and a beta silicon carbide overlay layer epitaxially related to the substrate, the beta silicon carbide layer being unpolytyped, single crystal, uncracked, without twins, and having integrated circuit quality surface morphology. Preferably, the substrate is a single crystal of titanium carbide, which is the same cubic lattice-type as beta silicon carbide with a lattice parameter different from that of beta silicon carbide by less than about 1%. Additionally, the thermal expansion coefficients of beta silicon carbide and titanium carbide are nearly the same, minimizing the creation of thermal stresses during cooling and heating. The beta silicon carbide is useful in fabricating semiconductor devices for use at much higher temperatures than is silicon, and for use at high power levels, at high frequencies, and in radiation hardened applications. The device base may be fabricated by any suitable technique, including reactive deposition and chemical vapor deposition.

An ohmic contact structure and method of forming the same are described which yield a true non-rectifying Schottky junction between a metallic material and a semiconductor material. The two materials are selected so that they satisfy the theoretical requirements for an ideal Schottky junction, with the work function of the metallic material less than that of an n-type semiconductor material and greater than that of a p-type simiconductor material. One of the materials is deposited upon the other by means of an epitaxial process, with the two materials being selected such that the difference in their lattice parameters is less than about 10%, and preferably less than about 5%. This process reduces or entirely eliminates the previous requirement for doping the contact region, and also eliminates a heat cycle that has previously been necessary to fabricate a non-rectifying junction.

Method of making ohmic contact structure

A semiconductor device component, and process for preparation thereof, wherein current flowing in a vertical channel of semiconductor material is controlled by metallic gates laterally disposed on either side of the channel. Insulator layers are positioned overlying and underlying each gate, to reduce parasitic capacitance which would otherwise be present if the metallic gate material were in contact with overlying and underlying semiconductor material. Reduction of the capacitance allows the use of wider gate strips, thereby reducing the series resistance to an external gate contact. These changes significantly improve the high-power, high-frequency performance of the device component, as compared with permeable base transistors.

Vertical channel field effect transistor

A chemical vapor deposition (CVD) reactor system is described comprising a substantially vertical reactor tube having a gas inlet and a gas outlet, a pedestal mounted within the reactor tube having a structure for securing a substrate thereto so that a surface of the substrate is exposed downward, and apparatus for providing a gas mixture to the reactor tube, the gas mixture being introduced into the reactor tube via the gas inlet and subsequently withdrawn via the gas outlet, the gas inlet and outlet being positioned, with respect to the substrate, below and above, respectively. The gas mixture is maintained in substantially uniform plug flow as it is directed into close proximity to the exposed surface of the substrate. This permits the CVD growth of physically uniform layers, both in terms of thickness and composition, having low contamination concentrations over large substrate surface areas.

Inverted positive vertical flow chemical vapor deposition reactor chamber

A directionally solidified, optically conductive eutectic system and method of forming the same. A Type II eutectic which divides into fiber and matrix phases when directionally solidified consists of a fiber phase having a lesser molecular weight but higher refractive index than the matrix phase. The resulting fiber array is optically conductive, and may be used to advantage in applications such as CRT screens, waveguides, fiber optic image intensifiers, and lasers.

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Newbury Park, CA, United States of America

James D Parsons