Abstract: The present invention provides a method for producing an n-type Group III nitride semiconductor product having a high Si concentration and exhibiting favorable crystallinity. In the production method, specifically, an AlN buffer layer is formed on a sapphire substrate by MOCVD, and then a first layer (thickness: 2 ?m) is formed from undoped GaN on the buffer layer by MOCVD at 1,140° C. Subsequently, a second layer (thickness: 200 nm) is formed from SiO2 on the first layer by plasma CVD, and then the second layer is removed by use of BHF (buffered hydrofluoric acid). Next, a GaN layer (thickness: 50 nm) is grown, by MOCVD at 1,140° C., on the first layer exposed by removal of the second layer without supply of an n-type dopant gas. Thus, on the first layer is provided a third layer formed of n-type GaN doped with Si at a high concentration and exhibiting favorable crystallinity.

Abstract: The present invention provides a method for producing an n-type Group III nitride semiconductor product having a high Si concentration and exhibiting favorable crystallinity. In the production method, specifically, an AlN buffer layer is formed on a sapphire substrate by MOCVD, and then a first layer (thickness: 2 ?m) is formed from undoped GaN on the buffer layer by MOCVD at 1,140° C. Subsequently, a second layer (thickness: 200 nm) is formed from SiO2 on the first layer by plasma CVD, and then the second layer is removed by use of BHF (buffered hydrofluoric acid). Next, a GaN layer (thickness: 50 nm) is grown, by MOCVD at 1,140° C., on the first layer exposed by removal of the second layer without supply of an n-type dopant gas. Thus, on the first layer is provided a third layer formed of n-type GaN doped with Si at a high concentration and exhibiting favorable crystallinity.

Abstract: A field-effect transistor which comprises a buffer layer and a barrier layer each of which is made of a Group III nitride compound semiconductor and has a channel at the interface inside of the buffer layer to the barrier layer, wherein the barrier layer has multiple-layer structure comprising an abruct interface providing layer which composes the lowest semiconductor layer in said barrier layer and whose composition varies rapidly at the interface of said buffer layer, and an electrode connection plane providing layer which constructs the uppermost semiconductor layer and whose upper surface is formed flat.

Abstract: An epitaxial crystal for a field effect transistor which has a nitride-based III-V group semiconductor epitaxial crystal grown on a SiC single crystal base substrate having micropipes by use of an epitaxial growth method, wherein at least a part of the micropipes spreading from the SiC single crystal base substrate into the epitaxial crystal terminate between an active layer of the transistor and the SiC single crystal base substrate.

Abstract: A semiconductor device having an AlGaN—GaN heterojunction structure including an AlGaN layer and a GaN layer which device exhibits no changes over time in sheet resistance. As shown in FIG. 1, in a semiconductor device having an AlGaN—GaN heterojunction structure including an AlGaN layer 1 and a GaN layer 2, when the Al molar fraction of AlGaN (x %) and the thickness of the AlGaN layer (y nm) satisfy the relations: x+y<55, 25?x?40, and y?10, y is smaller than the critical thickness, whereby no cracks are generated in the AlGaN layer. Therefore, the invention provides a semiconductor device exhibiting virtually no changes over time in sheet resistance despite high Al molar fraction.

Abstract: An electronic device includes a substrate; a single-crystalline first buffer layer, disposed on the substrate, containing a semiconductor represented by the formula AlxGa1?xN; a non-single-crystalline second buffer layer, disposed on the first buffer layer, containing a semiconductor represented by the formula AlyGa1?yN; and an undoped base layer, disposed on the second buffer layer, containing GaN, wherein 0<×?1 and 0?y?1. The first buffer layer is formed at a temperature of 1000° C. to 1200° C. The second buffer layer is formed at a temperature of 350° C. to 800° C. The substrate contains SiC. The second buffer layer has a thickness of 5 to 20 nm.

Abstract: Provided is an HFET exhibiting reduced buffer leakage current. The HFET of the present invention includes an SiC substrate, an AlN layer, a graded AlGaN layer, a GaN layer, an AlGaN layer (Al compositional proportion: 20%), a source electrode, a gate electrode, and a drain electrode, wherein the AlN layer, the graded AlGaN layer, the GaN layer, and the AlGaN (Al: 20%) layer are successively stacked on the substrate, and the electrodes are formed on the AlGaN (Al: 20%) layer so as to be separated from one another. In the graded AlGaN layer, the Al compositional proportion gradually decreases from 30% (at the side facing the AlN layer) to 5% (at the side facing the GaN layer). Provision of the graded AlGaN layer reduces strain between the AlN layer and the GaN layer. Therefore, the HFET exhibits reduced buffer leakage current.

Abstract: A field-effect transistor includes a channel layer having a channel and a carrier supply layer, disposed on the channel layer, containing a semiconductor represented by the formula AlxGa1-xN, wherein x is greater than 0.04 and less than 0.45. The channel is formed near the interface between the channel layer and the carrier supply layer or depleted, the carrier supply layer has a band gap energy greater than that of the channel layer, and x in the formula AlxGa1-xN decreases monotonically with an increase in the distance from the interface. The channel layer may be crystalline of gallium nitride. The channel layer may be undoped. X of the formula AlxGa1-xN of the carrier supply layer is greater than or equal to 0.15 and less than or equal to 0.40 at the interface.

Abstract: A field-effect transistor which comprises a buffer layer and a barrier layer each of which is made of a Group III nitride compound semiconductor and has a channel at the interface inside of the buffer layer to the barrier layer, wherein the barrier layer has multiple-layer structure comprising an abruct interface providing layer which composes the lowest semiconductor layer in said barrier layer and whose composition varies rapidly at the interface of said buffer layer, and an electrode connection plane providing layer which constructs the uppermost semiconductor layer and whose upper surface is formed flat.

Abstract: An electronic device includes a substrate; a single-crystalline first buffer layer, disposed on the substrate, containing a semiconductor represented by the formula AlxGa1-xN; a non-single-crystalline second buffer layer, disposed on the first buffer layer, containing a semiconductor represented by the formula AlyGa1-yN; and an undoped base layer, disposed on the second buffer layer, containing GaN, wherein 0<×?1 and 0?y?1. The first buffer layer is formed at a temperature of 1000° C. to 1200° C. The second buffer layer is formed at a temperature of 350° C. to 800° C. The substrate contains SiC. The second buffer layer has a thickness of 5 to 20 nm.

Abstract: An epitaxial crystal for a field effect transistor which has a nitride-based III-V group semiconductor epitaxial crystal grown on a SiC single crystal base substrate having micropipes by use of an epitaxial growth method, wherein at least a part of the micropipes spreading from the SiC single crystal base substrate into the epitaxial crystal terminate between an active layer of the transistor and the SiC single crystal base substrate.

Abstract: A field-effect transistor includes a channel layer having a channel and a carrier supply layer, disposed on the channel layer, containing a semiconductor represented by the formula AlxGa1-xN, wherein x is greater than 0.04 and less than 0.45. The channel is formed near the interface between the channel layer and the carrier supply layer or depleted, the carrier supply layer has a band gap energy greater than that of the channel layer, and x in the formula AlxGa1-xN decreases monotonically with an increase in the distance from the interface. The channel layer may be crystalline of gallium nitride. The channel layer may be undoped. X of the formula AlxGa1-xN of the carrier supply layer is greater than or equal to 0.15 and less than or equal to 0.40 at the interface.