Coorstek Kk

Covalent Materials Corporation

Covalent Material Corporation

Kenichi Eriguchi

Yoshihisa Abe

Jun Komiyama

Hiroshi Oishi

Akira Yoshida

Shunichi Suzuki

Noriko Omori

Tomoko Watanabe

The present invention provides a nitride semiconductor substrate suitable for a high frequency device. The nitride semiconductor substrate has a substrate, a buffer layer made of group 13 nitride semiconductors, and an active layer made of group 13 nitride semiconductors in this order, wherein the substrate is composed of a first substrate made of polycrystalline aluminum nitride, and a second substrate made of Si single crystal having a specific resistance of 100 &#x3a9;&#xb7;cm or more, formed on the first substrate, the average particle size of AlN constituting the first substrate is 3 to 9 &#x3bc;m, and preferably, the second substrate grown by the MCZ method has an oxygen concentration of 1E+18 to 9E+18 atoms/cmand a specific resistance of 100 to 1000 &#x3a9;&#xb7;cm.

Nitride semiconductor substrate and method of manufacturing the same

The characteristic of Fe-doped HEMTs is improved. The invention provides a nitride semiconductor substrate having a substrate, a buffer layer made of nitride semiconductors on the substrate, and an active layer composed of nitride semiconductor layers on the buffer layer; the buffer layer containing Fe, the Fe having a concentration profile in which the Fe concentration increases monotonically and gradually in the thickness direction of the buffer layer from an interface between the substrate and the buffer layer, has a maximum value within 2&#xd7;10to 1.1&#xd7;10atoms/cminclusive, and decreases monotonically and gradually toward an interface between the buffer layer and the active layer, and the point of the maximum value being within &#xb1;50 nm from the midpoint in the thickness direction of the buffer layer, and being 500 nm or more away from the interface between the buffer layer and the active layer.

Nitride semiconductor substrate

A nitride semiconductor substrate can effectively reduce leakage current in the vertical direction. The nitride semiconductor substrate comprises a buffer layer and an operation layer, both of which are made of nitride semiconductor, deposited on a silicon single crystal substrate, wherein the buffer layer comprises a single-layered first initial layer in contact with the silicon single crystal layer, and a single-layered second initial layer in contact with the first initial layer, the first initial layer is made of AlN, the second initial layer is made of AlGaN (0.12&#x2264;z&#x2264;0.65), and in an X-Y graph where the X-axis denotes z&#xd7;100 and the Y-axis denotes carbon concentration in the second initial layer, X ranges from 12 to 65 and Y is within a range between Y=1E+17&#xd7;exp(&#x2212;0.05&#xd7;X) and Y=1E+21&#xd7;exp(&#x2212;0.05&#xd7;X).

A compound semiconductor substrate according to the present invention includes a compound semiconductor layer formed on one main surface of a ground substrate via a seed layer, wherein the ground substrate is formed of a sintered body, the seed layer is formed of a single crystal, the compound semiconductor layer includes a structure having a buffer layer and an active layer that are sequentially crystal-grown on the seed layer, a thermal expansion coefficient of the sintered body is 0.7 times or more and 1.4 times or less an average thermal expansion coefficient of the entire compound semiconductor layer, and an FWHM of an X-ray diffraction peak of the buffer layer obtained by an X-ray diffraction rocking curve measurement is 800 arcsec or less.

Compound semiconductor substrate

The present invention provides a nitride semiconductor substrate having an initial nitride and a nitride semiconductor sequentially stacked on one principal plane of a base substrate, wherein the nitride semiconductor substrate comprises recesses depressed from an interface between the base substrate and the initial nitride toward the base substrate along one arbitrary cross section; the recesses each have a diameter of 6 nm or more and 60 nm or less and are formed at a density of 3&#xd7;10pieces/cmor more and 1&#xd7;10pieces/cmor less; and the recess preferably has a depth of 3 nm or more and 45 nm or less from the interface between the base substrate and the initial nitride toward the base substrate.

Nitride semiconductor substrate having recesses at interface between base substrate and initial nitride

A nitride semiconductor substrate is provided which is suitable for a high withstand voltage power device and prevents a warp and a crack from generating in a Si substrate when forming a thick nitride semiconductor layer on the substrate. A nitride semiconductor substrateis prepared in such a manner that a buffer layerand a semiconductor active layereach comprising a group 13 nitride are stacked one by one on one principal plane of a Si single crystal substrate, the one principal plane has an offset angle of 0.1&#xb0; to 1&#xb0; or &#x2212;1&#xb0; to &#x2212;0.1&#xb0; with respect to a (111) plane, an average dopant concentration in a bulk is 1&#xd7;10to 1&#xd7;10cm, the Si single crystal substratehas a SiOfilm on the back, and the total thickness of the buffer layerand the semiconductor active layeris 4 to 10 &#x3bc;m.

A solution is formation of a nitride semiconductor layer on one principal plane of a single crystal substrate through a first layer. Upon selecting arbitrary three places in a radial direction from a cross section cleaved in a diameter portion and observing an interface between the first layer and the nitride semiconductor layer by taking a width of at least 500 nm in the radial direction, a value is within the range of 6 nm or more and 15 nm or less in a mean value of the three places with regard to a difference between a maximum height of a convex top portion and a minimum height of a concave bottom portion of the first layer in a thickness direction from the single crystal substrate toward the nitride semiconductor layer. A value is 10 nm or more and 25 nm or less in the mean value.

A nitride semiconductor substrate suitable for a normally-off type high breakdown-voltage device and a method of manufacturing the substrate are provided allowing both a higher threshold voltage and improvement in current collapse. In a nitride semiconductor substratehaving a substratea buffer layerformed on one principal plane of the substratean intermediate layerformed on the buffer layeran electron transport layerformed on the intermediate layerand an electron supply layerformed on the electron transport layerthe intermediate layerhas a thickness of 200 nm to 1500 nm and a carbon concentration of 5&#xd7;10atoms/cmto 1&#xd7;10atoms/cmand is of AlGaN (0.05&#x2266;x&#x2266;0.24), and the electron transport layerhas a thickness of 5 nm to 200 nm and is of AlGaN (0&#x2266;y&#x2266;0.04).

A nitride semiconductor substrate is provided in which leak current reduction and improvement in current collapse are effectively attained when using Si single crystal as a base substrate. The nitride semiconductor substrate is such that an active layer of a nitride semiconductor is formed on one principal plane of a Si single crystal substrate through a plurality of buffer layers made of a nitride, in the buffer layers, a carbon concentration of a layer which is in contact with at least the active layer is from 1&#xd7;10to 1&#xd7;10atoms/cm, a ratio of a screw dislocation density to the total dislocation density is from 0.15 to 0.3 in an interface region between the buffer layer and the active layer, and the total dislocation density in the interface region is 15&#xd7;10cmor less.

A compound semiconductor substrate which inhibits the generation of a crack or a warp and is preferable for a normally-off type high breakdown voltage device, arranged that a multilayer buffer layerin which AlGaN single crystal layers (0.6&#x2266;X&#x2266;1.0)containing carbon from 1&#xd7;10atoms/cmto 1&#xd7;10atoms/cmand AlGaN single crystal layers (0.1&#x2266;y&#x2266;0.5) 22 containing carbon from 1&#xd7;10atoms/cmto 1&#xd7;10atoms/cmare alternately and repeatedly stacked in order, and a nitride active layerprovided with an electron transport layerhaving a carbon concentration of 5&#xd7;10atoms/cmor less and an electron supply layerare deposited on a Si single crystal substratein order. The carbon concentrations of the AlGaN single crystal layersand that of the AlGaN single crystal layersrespectively decrease from the substrateside towards the above-mentioned active layerside. In this way, the compound semiconductor substrate is produced.

Compound semiconductor substrate comprising a multilayer buffer layer

The present invention provides a compound semiconductor substrate, including: a single-crystal silicon substrate having a crystal face with (111) orientation; a first buffer layer which is formed on the single-crystal silicon substrate and is constituted of an AlGaN single crystal (0&#x3c;x&#x2266;1); a second buffer layer which is formed on the first buffer layer and is composed of a plurality of first unit layers each having a thickness of from 250 nm to 350 nm and constituted of an AlGaN single crystal (0&#x2266;y&#x3c;0.1) and a plurality of second unit layers each having a thickness of from 5 nm to 20 nm and constituted of an AlGaN single crystal (0.9&#x3c;z&#x2266;1), said pluralities of first and second unit layers having been alternately superposed; and a semiconductor device formation region which is formed on the second buffer layer and includes at least one nitride-based semiconductor single-crystal layer. The compound semiconductor substrate according to the invention is suitable for use in electronic devices such as HEMTs (high electron mobility transistors).

Growing community of inventors

Hadano, Japan

Kenichi Eriguchi