Semi-insulating silicon carbide without vanadium domination

a silicon carbide and silicon carbide technology, applied in the microwave field, can solve the problems of reducing yield, negatively affecting the crystalline quality of the resulting material, and generally too conductive silicon carbide grown by most techniques, and achieve the effect of high frequency operation

US20010023945A1Inactive Publication Date: 2001-09-27CREE INC
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Patent Information

Authority / Receiving Office
US · United States
Patent Type
Applications(United States)
Current Assignee / Owner
Publication Date
2001-09-27
Estimated Expiration
Not applicable · inactive patent

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Abstract

A semi-insulating bulk single crystal of silicon carbide is disclosed that has a resistivity of at least 5000 .OMEGA.-cm at room temperature and a concentration of trapping elements that create states at least 700 meV from the valence or conduction band that is below the amounts that will affect the resistivity of the crystal, preferably below detectable levels. A method of forming the crystal is also disclosed, along with some resulting devices that take advantage of the microwave frequency capabilities of devices formed using substrates according to the invention.
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Description

[0001] This is a continuation-in-part of Ser. No. 09 / 757,950 filed Jan. 10, 2001, which is a continuation of Ser. No. 09 / 313,802 filed May 18, 1999, now U.S. Pat. No. 6,218,680. The present invention relates to the growth of high quality silicon carbide crystals for specific purposes, and in particular relates to the production of high quality semi-insulating silicon carbide substrates that are useful in microwave devices.BACKGROUND OF THE INVENTION

[0003] The term "microwaves" refers to electromagnetic energy in frequencies covering the range of about 0.1 gigahertz (GHz) to 1,000 GHz with corresponding wavelengths from about 300 centimeters to about 0.3 millimeters. Although "microwaves" are perhaps most widely associated by the layperson with cooking devices, those persons familiar with electronic devices recognize that the microwave frequencies are used for a large variety of electronic purposes and in corresponding electronic devices, including various communication devices, and ...

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Embodiment Construction

[0071] Two wafers of semi-insulating SiC were examined at the Air Force Research Laboratory at Dayton, Ohio (Wright-Patterson Air Force Base), with high temperature Hall effect and SIMS. No understandable results were available from one of the wafers (possibly because of unsatisfactory ohmic contacts), but two Hall samples from the second wafer both gave the same results, giving a reasonable confidence level in those results.

[0072] Both wafers were insulating at room temperature. The measurable wafer was thermally activated at elevated temperatures and the carrier concentration was measurable, which is not always possible in semi-insulating material because of the low mobilities due to the high temperatures involved. The carrier concentration was around 10.sup.15 cm.sup.-3 at 1000K where the resistivity was about 103 .OMEGA.-cm. Such carrier concentration is about one to two orders of magnitude lower than that seen in conventional semi-insulating material or vanadium doped material ...