Semiconductor device and method of manufacturing the device
View Patent ↗A semiconductor device includes a substrate; a carrier traveling layer formed on the substrate, made of first group III nitride semiconductor, and containing carriers traveling in a direction along a principal surface of the substrate; a barrier layer formed on the carrier traveling layer and made of second group III nitride semiconductor having a wider band gap than the first group III nitride semiconductor; and an electrode formed on the barrier layer. The device further includes a cap layer formed on the barrier layer at a side of the electrode, and made of third group III nitride semiconductor containing a mixture of single crystals and polycrystals.
1. A semiconductor device comprising:
a substrate;
a carrier traveling layer formed on the substrate, made of first group III nitride semiconductor, and containing carriers traveling in a direction along a principal surface of the substrate;
a barrier layer formed on the carrier traveling layer and made of second group III nitride semiconductor having a wider band gap than the first group III nitride semiconductor;
an electrode formed on the barrier layer; and
a cap layer formed on the barrier layer at a side of the electrode, and made of third group III nitride semiconductor containing a mixture of single crystals and polycrystals,
wherein the single crystals takes over a crystal structure of the barrier layer.
2. The semiconductor device of claim 1 , wherein
the single crystals are disposed on an interface with the barrier layer.
3. The semiconductor device of claim 2 , wherein
the single crystals are formed non-uniformly in a thickness along the interface with the barrier layer.
4. The semiconductor device of claim 1 , wherein
the single crystals comprises a single crystal layer disposed on the interface with the barrier layer and an insular single crystal portion disposed on the single crystal layer.
5. The semiconductor device of claim 1 , wherein
the cap layer is made of group III nitride semiconductor containing aluminum (Al).
6. The semiconductor device of claim 5 , wherein
a surface of the cap layer opposite to the substrate is oxidized.
7. The semiconductor device of claim 1 , wherein
the cap layer is made of aluminum nitride (AlN), the barrier layer is made of Al x Ga 1-x N, where 0<x≦1, and the carrier traveling layer is made of GaN.
8. The semiconductor device of claim 1 , further comprising:
a spacer layer provided between the carrier traveling layer and the barrier layer, and made of single crystal aluminum nitride (AlN).
9. The semiconductor device of claim 1 , further comprising:
a p-type group III nitride semiconductor layer provided between the barrier layer and the electrode.
10. The semiconductor device of claim 9 , wherein
the p-type group III nitride semiconductor layer is made of Al x Ga 1-x N, wherein 0≦x≦1.
11. The semiconductor device of claim 1 , further comprising:
an insulating layer provided between the barrier layer and the electrode.
12. The semiconductor device of claim 11 , wherein
the insulating layer is made of aluminum oxide (Al 2 O 3 ).
13. The semiconductor device of claim 1 , wherein
a portion of the barrier layer under the electrode has a smaller thickness than the side of the electrode.
14. The semiconductor device of claim 1 , wherein
a sheet carrier concentration in the carrier traveling layer is more than 1×10 13 cm −2 .
15. The semiconductor device of claim 1 , wherein the single crystals have higher etching resistivity to an alkaline solution than the polycrystals.
16. The semiconductor device of claim 1 , wherein a crystalline size of the single crystals is greater than crystal sizes of the polycrystals.
17. The semiconductor device of claim 2 , wherein
the single crystals comprise a plurality of insular single crystal portions.
18. The semiconductor device of claim 17 , wherein the plurality of insular single crystal portions are covered by the polycrystals.