In a group III nitride-type field effect transistor, the present invention reduces a leak current component by conduction of residual carriers in a buffer layer, and achieves improvement in a break-down voltage, and enhances a carrier confinement effect (carrier confinement) of a channel to improve pinch-off characteristics (to suppress a short channel effect). For example, when applying the present invention to a GaN-type field effect transistor, besides GaN of a channel layer, a composition-modulated (composition-gradient) AlGaN layer in which aluminum composition reduces toward a top gradually or stepwise is used as a buffer layer (hetero buffer). To gate length Lg of a FET to be prepared, a sum a of layer thicknesses of an electron supply layer and a channel layer is selected so as to fulfill Lg/a≧5, and in such a case, the layer thickness of the channel layer is selected in a range of not exceeding 5 times (about 500 Å) as long as a de Broglie wavelength of two-dimensional electron gas accumulated in the channel layer in room temperature.

Field effect transistor, and multilayered epitaxial film for use in preparation of field effect transistor

This invention provides a thermoelectric conversion material in which at least a part of an insulating material contained in the thermoelectric conversion material has a particle diameter which is not more than the mean free path of phonon of the insulating material, or the dispersion spacing between the insulating materials is not more than the mean free path of phonon of the thermoelectric conversion material. There is also provided a process for producing a thermoelectric conversion material, comprising a composite nanoparticle formation step of reductively precipitating raw material particles of a thermoelectric conversion material on nanoparticles formed of an insulating material, and heat treating the assembly to form composite nanoparticles comprising the nanoparticles covered with the thermoelectric conversion material, and a sintering step of filling the composite nanoparticles and sintering the composite nanoparticles.

Thermoelectric conversion material and process for producing the same

Disclosed is a group III nitride semiconductor device wherein leakage current from a Schottky electrode is reduced. In a high-electron-mobility transistor (1), a supporting substrate (3) is composed of AlN, AlGaN and GaN. An AlYGa1-YN epitaxial layer (5) has a surface roughness (Rms) of not more than 0.25 nm, and this surface roughness is defined by a 1 μm square area. A GaN epitaxial layer (7) is formed between the AlYGa1-YN supporting substrate (3) and the AlYGa1-YN epitaxial layer (5). A Schottky electrode (9) is formed on the AlYGa1-YN epitaxial layer (5). A first ohmic electrode (11) is formed on the AlYGa1-YN epitaxial layer (5), and a second ohmic electrode (13) is formed on the AlYGa1-YN epitaxial layer (5). One of the first and second ohmic electrodes (11, 13) is a source electrode, and the other is a drain electrode. The Schottky electrode (9) is a gate electrode of the high-electron-mobility transistor (1).

Group III Nitride Semiconductor Device and Epitaxial Substrate

Method for producing a nanostructure based on interconnected nanowires, nanostructure and use as thermoelectric converter The nanostructure comprises two arrays of nanowires made from respectively n-doped and p-doped semi-conducting material. The nanowires of the first array, for example of n type, are formed for example by VLS growth. A droplet of electrically conducting material that acted as catalyst during the growth step remains on the tip of each nanowire of the first array at the end of growth. A nanowire of the second array is then formed around each nanowire of the first array by covering a layer of electrically insulating material formed around each nanowire of the first array, and the associated droplet, with a layer of p-type semi-conducting material. A droplet thus automatically connects a nanowire of the first array with a single coaxial nanowire of the second array. This type of nanostructure can be used in particular to form a thermoelectric converter.

Method for producing a nanostructure based on interconnected nanowires, nanostructure and use as thermoelectric converter

Disclosed is a semiconductor device having improved performance with an improved trade-off between a withstand voltage and on-resistance. In the semiconductor device, a first n-type semiconductor layer (21'), a second n-type semiconductor layer (23), a p-type semiconductor layer (24), and a third n-type semiconductor layer (25') are laminated in this order on a substrate (1). A drain electrode (13) is in ohmic-contact with the first n-type semiconductor layer (21'), and a source electrode (12) is in ohmic-contact with the third n-type semiconductor layer (25'). A via hole that reaches the second n-type semiconductor layer (23) from the third n-type semiconductor layer (25') is filled with a gate electrode (14), and is bonded to the upper surface of the second n-type semiconductor layer (23), the side surface of the p-type semiconductor layer (24) and the side surface of the third n-type semiconductor layer (25'). The second n-type semiconductor layer (23) has a composition that changes from the drain electrode (13) side toward the source electrode (12) side in the direction perpendicular to the flat surface of the substrate (1), and contains a donor impurity.

Semiconductor device and field effect transistor

PROBLEM TO BE SOLVED: To provide a thermoelectric conversion apparatus having a pair of thermoelectric conversion excellent in heat resistance at a high temperature junction and capable of being used in a temperature range in which good thermoelectric conversion efficiency is provided. SOLUTION: A thermoelectric conversion apparatus 1 comprises a pair of thermoelectric conversion devices 2 having a p-type thermoelectric semiconductor device 2p and an n-type thermoelectric semiconductor device 2n electrically connected to each other through a high temperature end electrode 4. A high temperature end junction layer 3 mainly made of Ge and having a thickness of 10 to 300μm is formed on a high temperature end-side paired devices junction. Furthermore, when the p-type and n-type thermoelectric semiconductor devices 2p and 2n are electrically connected to each other through the high temperature end electrode 4, they are soldered at the high temperature end-side paired devices junction by using a solder material mainly made of Ge.

Thermoelectric conversion apparatus and thermoelectric its manufacture

PROBLEM TO BE SOLVED: To provide a large capacity thermoelectric conversion module capable of being in close contact with a curved surface and to provide method for manufacturing it accurately, easily and economically. SOLUTION: N-type semiconductor elements 13 and P-type semiconductor elements 14 are alternately inserted into successive holes of a honey-comb structure 11 having many through holes, and after clearances are filled with an easily deformable filler 15 and the honey-comb structure 11 is cut into a desired shape, the ends of the semiconductor elements exposed at the upper and lower surfaces are alternately connected by electrodes 16 to alternately connect all of the N-type semiconductor elements 13 and P-type semiconductor elements 14 in cascade connection.

Thermoelectric conversion module and manufacture thereof

PROBLEM TO BE SOLVED: To accurately and easily manufacture a thermoelectric conversion module which adheres to the curved plane and does not contaminate the surrounding by inserting a semiconductor fine strip into the penetrating hole of a honeycomb structure, filling the space, positioning and holding the semiconductor fine strip and cutting the strip. SOLUTION: An N-type semiconductor fine strip 23, which is formed by adding P by a density of 0.2wt.% as N-type dopant to the composition of Si 0.8 Ge 0.2 , and a P-type semiconductor fine strip 24, which is formed by adding B by a density of 0.05wt.% as P-type dopant to the composition of Si 0.8 Ge 0.2 , are inserted into the adjacent penetrating holes 22 of a honeycomb structure 21. Then, the space between the penetrating hole 22 of the honeycomb structure 21 and the semiconductor fine strips 23 and 24 is filled with filler 25 so as to hold the fine strips. A thermoelectric conversion module body 26 is formed by cutting the honeycomb structure 21 along the plane L which is vertical to the penetrating hole, and the adjacent N-type semiconductor devices 27 and 28 are cascade-connected by electrode 41 and 42 formed of metal fine strip. Therefore, when the filler 25 is selectively removed, a large capacity thermoelectric conversion module which has a discretionary curved plane is easily manufactured. COPYRIGHT: (C)1997,JPO

Manufacture of thermoelectric conversion module

PROBLEM TO BE SOLVED: To provide a method for easily and efficiently manufacture P-type thermoelectric converting materials in which CoSb3 is used as main components, a small amount of Fe is included as dopant for deciding a conductive type, and a stable P-type is indicated, and high performance can be obtained, electrical conductivity can be increased, chemical stability can be realized, and fluctuation due to the fluctuation of composition can be reduced by using a general baking process. SOLUTION: The chemical composition of the main components of P-type thermoelectric converting materials is represented by CoFexSby (0.001<x<0.6, 2.7<y<5.7), and the oxygen contents are set to 0.08 mol or less with respect to CoFexSby of 1 mol. Material powder, in which the chemical composition of main components is expressed by CoFexSby (0.001<x<0.6, 2.7<y<5.7) is baked in a reducing atmosphere such as hydrogen or material powder, in which the chemical composition of the main components is expressed by Co1-xFexSby (0.001<x<0.4, 2.7<y<3.4), and oxygen contents are 0.08 mol or less with respect to 1 mol is backed in a nonoxidizing atmosphere such as nitrogen.

P-type thermoelectric converting material and manufacture of the same

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Thermoelectric conversion apparatus and thermoelectric its manufacture

Thermoelectric conversion module and manufacture thereof

Manufacture of thermoelectric conversion module

P-type thermoelectric converting material and manufacture of the same