COMPOUND SEMICONDUCTOR DEVICE AND METHOD FOR MANUFACTURING THE SAME

1 . A compound semiconductor device, comprising:

a substrate; and

a compound semiconductor layer disposed over the substrate,

wherein the compound semiconductor layer includes a first region having first conductivity-type carriers generated by activating a first impurity and also includes a second region having carriers at lower concentration as compared to the first region, the carriers being generated by activating a second impurity which is the same type as the first impurity.

2 . The compound semiconductor device according to claim 1 , wherein the first conductivity-type carriers are holes.

3 . The compound semiconductor device according to claim 2 , wherein the first impurity and the second impurity are Mg or C or Mg+C.

4 . The compound semiconductor device according to claim 1 , further comprising:

an electron travel layer located between the substrate and the compound semiconductor layer;

an electron supply layer located between the electron travel layer and the compound semiconductor layer;

a source electrode located over the electron travel layer;

a drain electrode located over the electron travel layer; and

a gate electrode located over the first region,

wherein the second region is located between the gate electrode and the drain electrode in plan view.

5 . The compound semiconductor device according to claim 4 , further comprising a field plate electrode located over the second region.

6 . The compound semiconductor device according to claim 1 , further comprising:

an electron travel layer located between the substrate and the compound semiconductor layer;

an electron supply layer located between the electron travel layer and the compound semiconductor layer;

an anode electrode located over the electron travel layer; and

a cathode electrode located over the electron travel layer,

wherein the first region and the second region are located between the anode electrode and the cathode electrode in plan view such that the first region is located on the anode electrode side and the second region is located on the cathode electrode side.

7 . The compound semiconductor device according to claim 1 , further comprising:

a lower compound semiconductor layer which is located between the substrate and the compound semiconductor layer and which has second conductivity-type carriers;

a gate electrode located over the first region;

a source electrode located over the second region;

an upper compound semiconductor layer which is located between the second region and the source electrode and which has the second conductivity-type carriers; and

a drain electrode located under the substrate.

8 . A power supply system including a compound semiconductor device, the compound semiconductor device comprising:

a substrate; and

a compound semiconductor layer disposed over the substrate,

wherein the compound semiconductor layer includes a first region having first conductivity-type carriers generated by activating a first impurity and also includes a second region having carriers at lower concentration as compared to the first region, the carriers being generated by activating a second impurity which is the same type as the first impurity.

9 . A high-frequency amplifier including a compound semiconductor device, the compound semiconductor device comprising:

a substrate; and

a compound semiconductor layer disposed over the substrate,

wherein the compound semiconductor layer includes a first region having first conductivity-type carriers generated by activating a first impurity and also includes a second region having carriers at lower concentration as compared to the first region, the carriers being generated by activating a second impurity which is the same type as the first impurity.

10 . A method for manufacturing a compound semiconductor device, comprising:

forming a compound semiconductor layer having an impurity over a substrate;

generating first conductivity-type carriers in such a manner that a first region of the compound semiconductor layer is irradiated with a laser beam at a first irradiation intensity and thereby the impurity in the first region is activated; and

generating the first conductivity-type carriers in such a manner that a second region of the compound semiconductor layer that is different from the first region is irradiated with a laser beam at a second irradiation intensity that is different from the first irradiation intensity and thereby the impurity in the second region is activated.

11 . The method according to claim 10 , wherein the first conductivity-type carriers are holes.

12 . The method according to claim 11 , wherein the impurity is Mg or C.

13 . The method according to claim 10 , further comprising: prior to forming of the compound semiconductor layer,

forming an electron travel layer over the substrate;

forming an electron supply layer over the electron travel layer;

forming a source electrode and a drain electrode over the electron travel layer; and

forming a gate electrode over the first region after forming the compound semiconductor layer,

wherein the second region is located between the gate electrode and the drain electrode in plan view.

14 . The method according to claim 13 , further comprising forming a field plate electrode over the second region.

15 . The method according to claim 10 , further comprising: prior to forming the compound semiconductor layer,

forming an electron travel layer over the substrate;

forming an electron supply layer over the electron travel layer; and

forming an anode electrode and a cathode electrode over the electron travel layer;

wherein the first region and the second region are located between the anode electrode and the cathode electrode in plan view such that the first region is located on the anode electrode side and the second region is located on the cathode electrode side.

16 . The method according to claim 10 , further comprising:,

forming a lower compound semiconductor layer having second conductivity-type carriers over the substrate prior to forming the compound semiconductor layer;

forming a gate electrode located over the first region;

forming an upper compound semiconductor layer having the second conductivity-type carriers over the second region;

forming a source electrode over the upper compound semiconductor layer; and

forming a drain electrode under the substrate.