Semiconductor device and method for manufacturing same
View Patent ↗A semiconductor device includes: a channel layer which is made of In p Al q Ga 1-p-q N (0≦p+q≦1, 0≦p, and 0≦q); a barrier layer which is formed on the channel layer and is made of In r Al s Ga 1-r-s N (0≦r+s≦1, 0≦r) having a bandgap larger than that of the channel layer; a diffusion suppression layer which is selectively formed on the barrier layer and is made of In t Al u Ga 1-t-u N (0≦t+u≦1, 0≦t, and s>u); a p-type conductive layer which is formed on the diffusion suppression layer and is made of In x Al y Ga 1-x-y N (0≦x+y≦1, 0≦x, and 0≦y) having p-type conductivity; and a gate electrode which is formed on the p-type conductive layer.
1. A semiconductor device comprising:
a first semiconductor layer which is made of In p Al q Ga 1-p-q N (0≦p+q≦1, 0≦p, and 0≦q);
a second semiconductor layer disposed on the first semiconductor layer, and is made of In r Al s Ga 1-r-s N (0≦r+s≦1, 0≦r) having a bandgap larger than that of the first semiconductor layer;
a third semiconductor layer which is selectively disposed on the second semiconductor layer, and is made of In t Al u Ga 1-t-u N (0≦t+u≦1, 0≦t, and s>u);
a fourth semiconductor layer disposed on the third semiconductor layer, and is made of In x Al y Ga 1-x-y N (0≦x+y≦1, 0≦x, and 0≦y) having p-type conductivity;
a gate electrode disposed on the fourth semiconductor layer; and
a source electrode and a drain electrode which are disposed directly on the second semiconductor layer.
2. The semiconductor device of claim 1 ,
wherein the third semiconductor layer has a variation in an amount of a p-type dopant per unit length in a film thickness direction, smaller than a variation in the fourth semiconductor layer.
3. The semiconductor device of claim 1 ,
wherein the second semiconductor layer includes a recessed portion formed on an upper surface thereof, and
the third semiconductor layer is disposed to fill at least a part of the recessed portion when viewed in a stacking direction.
4. The semiconductor device of claim 3 ,
wherein the third semiconductor layer is disposed to fill the recessed portion when viewed in the stacking direction.
5. The semiconductor device of claim 3 ,
wherein the third semiconductor layer has a structure in which a layer made of Al a Ga 1-a N (0<a≦1) and a layer made of GaN are stacked.
6. The semiconductor device of claim 5 ,
wherein the layer made of Al a Ga 1-a N (0<a≦1) in the third semiconductor layer has an Si concentration which is equal to or greater than 1×10 18 /cm 3 .
7. The semiconductor device of claim 5 ,
wherein the layer made of GaN in the third semiconductor layer has an Si concentration which is equal to or greater than 1×10 18 /cm 3 .
8. The semiconductor device of claim 1 ,
wherein a p-type dopant of the fourth semiconductor layer is Mg, and
the second semiconductor layer has an Mg concentration which is equal to or smaller than 1×10 19 /cm 3 in a portion that is in contact with the third semiconductor layer, and
the third semiconductor layer has an Mg concentration which is equal to or smaller than 1×10 19 /cm 3 in a portion that is in contact with the second semiconductor layer.
9. The semiconductor device of claim 1 ,
wherein the third semiconductor layer is made of GaN.
10. The semiconductor device of claim 1 ,
wherein the third semiconductor layer has an Si concentration which is equal to or greater than 1×10 18 /cm 3 .
11. The semiconductor device of claim 1 ,
wherein the second semiconductor layer has an Si concentration which is equal to or greater than 1×10 18 /cm 3 .
12. The semiconductor device of claim 1 ,
wherein the second semiconductor layer is formed by layering a layer not doped with Si and disposed on a side being in contact with the first semiconductor layer and a layer having an Si concentration equal to or greater than 1×10 18 /cm 3 and disposed on a side being in contact with the source electrode and the drain electrode.
13. The semiconductor device of claim 1 ,
wherein the fourth semiconductor layer is made of GaN.
14. The semiconductor device of claim 1 ,
wherein the fourth semiconductor layer is made of Al z Ga 1-z N (0<z≦1).
15. The semiconductor device of claim 1 ,
wherein the fourth semiconductor layer has a structure in which a layer made of Al z Ga 1-z N (0<z≦1) and disposed on a side being in contact with the third semiconductor layer and a layer made of GaN and disposed on a side being in contact with a gate electrode are stacked together.
16. The semiconductor device of claim 1 , further comprising a substrate on which the first semiconductor layer is disposed.
17. A method for manufacturing a semiconductor device, comprising the steps of:
forming a first semiconductor layer made of In p Al q Ga 1-p-q N (0≦p+q≦1, 0≦p, and 0≦q);
forming a second semiconductor layer made of In r Al s Ga 1-r-s N (0≦r+s≦1, 0≦r) having a bandgap larger than that of the first semiconductor layer, on the first semiconductor layer;
forming a third semiconductor layer made of In t Al u Ga 1-t-u N (0≦t+u≦1, 0≦t, and s>u) on the second semiconductor layer;
forming a fourth semiconductor layer made of In x Al y Ga 1-x-y N (0≦x+y≦1, 0≦x, and 0≦y) having p-type conductivity on the third semiconductor layer;
forming a gate electrode on the fourth semiconductor layer;
removing a region other than a region corresponding to the gate electrode, from the third semiconductor layer and the fourth semiconductor layer, after forming the fourth semiconductor layer; and
forming a source electrode and a drain electrode directly on the second semiconductor layer.
18. The method for manufacturing a semiconductor device of claim 17 , further comprising the step of forming a substrate on which the first semiconductor layer is disposed.