Nec Corporation

Renesas Electronics Corporation

Akio Wakejima

Hironobu Miyamoto

Yasuhiro Okamoto

Takashi Inoue

Yuji Ando

Tatsuo Nakayama

Yasuhiro Murase

Kazuki Ota

Naotaka Kuroda

Katsumi Yamanoguchi

Masahiro Tanomura

Kensuke Kasahara

Hidenori Shimawaki

Kohji Matsunaga

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&#x2265;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 &#x212b;) 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

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&#x2267;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 &#x212b;) as long as a de Broglie wavelength of two-dimensional electron gas accumulated in the channel layer in room temperature.

A power amplifier includes an amplifying circuit, and first through third transmission lines. The amplifying circuit amplifies an input signal having a fundamental frequency to generate a first amplified signal and a second amplified signal whose phase is opposed to the first amplified signal. The first transmission line adds a first group of phases, different in correspondence with a frequency, to the first amplified signal by using a left-handed material to generate a first transmission signal. The second transmission line adds a second group of phases, different in correspondence with a frequency, to the second amplified signal by using a right-handed material to generate a second transmission signal. The third transmission line overlaps the first and the second transmission signals to generate an output signal. The first and the second group of phases include a phase difference configured to weaken a second harmonic and a third harmonic.

High frequency power amplifier

A semiconductor device includes a semiconductor element having a rectangular two-dimensional geometry and serving as a heat source, a first heat sink section including the semiconductor element mounted thereon, and a second heat sink section joined to an opposite side of the first heat sink section that includes the semiconductor element. A relation among directional components of thermal conductivity is K&#x2267;K&#x3e;K, where directional components of a three-dimensional thermal conductivity of the heat sink section in X, Y, and Z directions are determined as Kxx, Kyy, and Kzz. A relation among directional components of a thermal conductivity of the second heat sink section is K&#x2267;K&#x3e;Kor K&#x2267;K&#x3e;K, where the directional components of the thermal conductivity of the second heat sink section in X, Y, and X directions are determined as K, K, and K

Semiconductor device and heat sink with 3-dimensional thermal conductivity

Disclosed is an HJFETwhich comprises: a channel layercomposed of InGaN (0&#x2266;y&#x2266;1); a carrier supply layercomposed of AlGaN (0&#x2266;x&#x2266;1), the carrier supply layerbeing provided over the channel layerand including at least one p-type layer; and a source electrodeS, a drain electrodeD and a gate electrodewhich are disposed facing the channel layerthrough the p-type layer, and provided over the carrier supply layer. The following relational expression is satisfied: 5.6&#xd7;10x&#x3c;N&#xd7;&#x3b7;&#xd7;t [cm]&#x3c;5.6&#xd7;10x, where x denotes an Al compositional ratio of said carrier supply layer, t denotes a thickness of said p-type layer, Ndenotes an impurity concentration, and &#x3b7; denotes an activation ratio.

Field effect transistor with reduced gate leakage current

Disclosed is an HJFETwhich comprises: a channel layercomposed of InGaN (0&#x2266;y&#x2266;1); a carrier supply layercomposed of AlGaN (0&#x2266;x&#x2266;1), the carrier supply layerbeing provided over the channel layerand including at least one p-type layer; and a source electrodeS, a drain electrodeD and a gate electrodewhich are disposed facing the channel layerthrough the p-type layer, and provided over the carrier supply layer. The following relational expression is satisfied: 5.6&#xd7;10x&#x3c;N&#xd7;&#x3b7;&#xd7;t [cm]&#x3c;5.6&#xd7;10x, where x denotes an Al compositional ratio of the carrier supply layer, t denotes a thickness of the p-type layer, Ndenotes an impurity concentration, and &#x3b7; denotes an activation ratio.

A semiconductor device, comprising: a semiconductor elementhaving a rectangular two-dimensional geometry and serving as a heat source; and a heat sink sectionhaving the semiconductor elementmounted thereon, wherein a relation among the directional components of said thermal conductivity is: Kzz&#x2267;Kyy&#x3e;Kxx, where directional components of three-dimensional thermal conductivity of the heat sink sectionin X, Y and Z directions are determined as Kxx, Kyy and Kzz, and where the longer side direction of the semiconductor elementis defined as X direction, the shorter side direction thereof is defined as Y direction and the thickness direction is defined as Z direction.

A field effect transistor () exhibiting good performance at high voltage operation and high frequency includes a first field plate electrode () and a second field plate electrode (). The second field plate electrode includes a shielding part () located in the region between the first field plate electrode and a drain electrode (), and serves to shield the first field plate electrode from the drain electrode. When in the cross sectional view in the gate length direction, the length in the gate length direction of an overlap region where the second field plate electrode () overlap the upper part of a structure including the first field plate electrode and a gate electrode () is designated as Lol, and the gate length is Lg, the relation expressed as 0 &#x2266;Lol/Lg&#x2266;1 holds.

Field effect transistor

A field effect transistor includes a layer structure made of compound semiconductor () provided on a semiconductor substrate () made of GaAs or InP, as an operation layer, and employs a first field plate electrode () and a second field plate electrode (). The second field plate electrode includes a shielding part () located in the region between the first field plate electrode and a drain electrode (), and serves to shield the first field plate electrode from the drain electrode. When, in the cross sectional view in the gate length direction, the length in the gate length direction of an overlap region, in which the second field plate electrode overlaps the upper part of a structure composed of the first field plate electrode and a gate electrode (), is designated as Lol, and the gate length is Lg, the relation expressed as 0&#x2266;Lol/Lg&#x2266;1 holds.

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Tokyo, Japan

Akio Wakejima