Kobe Steel Usa, Inc.

North Carolina State University

Kobe Development Corp.

Kalyankumar Das

Dale G Thompson, Jr

Robert J Nemanich

Trevor P Humphreys

Koichi Miyata

Kimitsugu Saito

Scott R Sahaida

Vasudev Venkatesan

An undoped highly-oriented diamond film is formed on a single crystalline silicon substrate, a p-type highly-oriented diamond film is formed on the insulating diamond film. An ohmic electrode is formed on said p-type semiconducting diamond film and an ohmic electrode is also formed on a n-type .beta.-SiC layer. The highly-oriented diamond films are grown by chemical vapor deposition and at least 80% of the surface area of said diamond film consists of either (100) or (111) crystal planes, and the differences {.DELTA..alpha., .DELTA..beta., .DELTA..gamma.} of Euler angles {.alpha., .beta., .gamma.}, which represent the orientations of the crystals simultaneously satisfy the following relations: .vertline..DELTA..alpha..vertline..ltoreq.5.degree., .vertline..DELTA..beta..vertline..ltoreq.5.degree. and .vertline..DELTA..gamma..vertline.5.degree. between adjacent crystal planes. The diamond hetero-junction rectifying element thus made has a high rectification ratio and heat resistance, and is suitable for mass production at low cost and on large scale.

Diamond hetero-junction rectifying element

A rectifying contact for use at high temperatures includes a semiconducting diamond layer and a doped amorphous silicon layer thereon. The amorphous silicon layer may be doped with either a p-type or n-type dopant. The semiconducting diamond may be a doped polycrystalline diamond layer or a natural IIb single crystal diamond. The amorphous silicon layer may be formed by sputter deposition from doped silicon targets. A subsequent heating of the thus formed rectifying contact lowers the forward resistance of the contact by activating additional dopant atoms within the amorphous silicon layer.

Amorphous silicon rectifying contact on diamond and method for making

A diamond transistor includes a base layer formed of a conductive material which is lattice matched to diamond, and which is embedded between two epitaxial diamond layers to form a monolithic heterostructure. An emitter contact is electrically connected to one diamond layer and a collector contact is electrically connected to the other diamond layer. The base layer may be a solid base layer, in which case a metal base transistor is formed. Alternatively, the base layer may be a patterned base layer having a grid of laterally spaced apart conductor lines, in which case a permeable base transistor is formed. Alternatively, the epitaxial diamond layers may be doped diamond layers of the same conductivity type. The epitaxial diamond layers may be undoped diamond layers formed between highly doped diamond layers, with the collector and emitter contacts being formed on the highly doped diamond layers to provide low resistance contacts. The transistor is preferably formed by epitaxially forming a first undoped diamond layer on a first heavily doped diamond layer. A metal base electrode is then epitaxially formed on the first undoped diamond layer. A second undoped diamond layer is epitaxially formed on the metal base electrode. A second heavily doped diamond layer is then formed on the second undoped diamond layer, and emitter and collector contacts are formed on the exposed faces of the respective heavily doped monocrystalline diamond layers.

Diamond metal base/permeable base transistor and method of making same

A vertical diamond field effect transistor includes a nondiamond substrate, preferably a heavily doped silicon substrate, having a diamond layer on one face thereof, a source contact on the diamond layer, a gate contact on the diamond layer adjacent the source contact, and a drain contact on the back face of the substrate. The diamond layer is preferably a single layer of large polycrystalline diamond grains, having a heavily doped region adjacent the silicon substrate. The gate and source contacts may extend across many polycrystalline diamond grains in the single layer of polycrystalline diamond grains. Alternatively, the source and gate contacts may be narrower than the average grain size of the polycrystalline diamond grains. Interdigitated source and gate fingers, narrower than the average polycrystalline diamond grain size, may also be provided. The single layer of polycrystalline grains may be formed on the silicon substrate. High performance vertical diamond field effect transistor devices are thereby provided.

Vertical diamond field effect transistor

A double heterojunction bipolar transistor includes diamond as the semiconductor material for the collector and emitter, while silicon carbide provides the base. Accordingly, the diamond is readily and reproducibly p-doped, and the silicon carbide may be fabricated by a solid state reaction to form an n-type intrinsic semiconductor. The base is preferably not so thick as to greatly increase transit time, yet sufficiently thick to prevent tunneling. In one embodiment single crystal diamond and single crystal silicon carbide are used in direct contact with each other. In another embodiment of the transistor, polycrystalline diamond is used, and a layer of insulating diamond is positioned between each face of the silicon carbide layer and the diamond layers. A method for fabricating the transistor includes depositing silicon on the diamond and annealing same so as to produce silicon carbide by a solid state reaction. The silicon carbide so produced is intrinsically n-type. Alternately, the silicon carbide may be directly deposited.

Diamond and silicon carbide heterojunction bipolar transistor

A rectifying contact includes a first semiconducting diamond layer, a second undoped diamond layer on the first layer, and a third relatively highly doped diamond layer on the second layer. The first semiconducting diamond layer may be formed on a supporting substrate. A bonding contact is preferably formed on the third relatively highly doped diamond layer for facilitating electrical connection thereto. The bonding contact is preferably a titanium carbide/gold bilayer. In one embodiment, an ohmic contact may be formed on the first semiconducting diamond layer by an electrically conductive substrate and an associated metal layer on an opposite side of the substrate from the semiconducting diamond layer. In another embodiment, an ohmic contact may be formed on the first semiconducting diamond layer by a fourth relatively highly doped diamond layer and an associated bonding contact on the fourth diamond layer. The relatively highly doped diamond layers may be formed by ion implantation, annealing, and an etch of a graphitized surface portion of the implanted diamond layers.

Diamond rectifying contact with undoped diamond layer

A rectifying contact for use at high temperatures including a monocrystalline semiconducting diamond layer on a substrate and a heteroepitaxial metal layer thereon. The metal layer has a lattice match with the diamond and is deposited on the diamond substantially in atomic registry therewith. The metal and diamond form a rectifying contact which has good mechanical adhesion and provides stable rectifying operation at elevated temperatures. The metal layer may be formed by deposition in an ultra-high vacuum. In alternate embodiments, the metal layer may be formed on a monocrystalline semiconducting diamond substrate or on at least one monocrystalline diamond area of a textured polycrystalline layer.

High temperature rectifying contact

A semiconductor device comprising a semiconducting diamond layer, (e.g. single crystal or polycrystalline), a refractory metal silicide layer adjacent the diamond layer for forming a rectifying contact therewith, and an annealed interface region between the diamond layer and the refractory metal silicide layer. The annealed interface region is preferably a non-abrupt interface comprising material selected from the group consisting of silicon carbide, the carbide of the refractory metal and mixtures thereof. The present invention also provides a method for making a rectifying contact on a semiconducting diamond layer comprising the steps of forming a refractory metal silicide on the diamond layer, and annealing the refractory metal silicide and diamond layer. Preferably, the step of annealing comprises the step of heating the diamond layer and refractory metal silicide at temperature of at least about 450.degree. C.

Growing community of inventors

Raleigh, NC, United States of America

Kalyankumar Das