Nitride Semiconductor Device And Production Method Thereof
A nitride semiconductor device according to the present invention includes a p-type nitride semiconductor layer, an n-type nitride semiconductor layer, and an active layer interposed between the p-type nitride semiconductor layer and the n-type nitride semiconductor layer. The p-type nitride semiconductor layer includes: a first p-type nitride semiconductor layer containing Al and Mg; and a second p-type nitride semiconductor layer containing Mg. The first p-type nitride semiconductor layer is located between the active layer and the second p-type nitride semiconductor layer, and the second p-type nitride semiconductor layer has a greater band gap than a band gap of the first p-type nitride semiconductor layer.
1 . A nitride semiconductor device comprising a p-type nitride semiconductor layer, an n-type nitride semiconductor layer, and an active layer interposed between the p-type nitride semiconductor layer and the n-type nitride semiconductor layer, wherein,
the p-type nitride semiconductor layer includes:
a first p-type nitride semiconductor layer containing Al and Mg; and
a second p-type nitride semiconductor layer containing Mg,
the first p-type nitride semiconductor layer being located between the active layer and the second p-type nitride semiconductor layer, and
the second p-type nitride semiconductor layer having a greater band gap than a band gap of the first p-type nitride semiconductor layer.
2 . The nitride semiconductor device of claim 1 , wherein the second p-type nitride semiconductor layer functions as a barrier layer for suppressing a carrier overflow from the active layer.
3 . The nitride semiconductor device of claim 1 , wherein,
the first p-type nitride semiconductor layer has an Al concentration of no less than 1×10 20 cm −3 and no more than 2×10 21 cm −3 ; and
a region of the first p-type nitride semiconductor layer in which the Al concentration is no less than 1×10 20 cm −3 and no more than 2×10 21 cm −3 has a thickness of 1 nm or more.
4 . The nitride semiconductor device of claim 1 , further comprising a non-doped nitride semiconductor layer which contains Al and which is located between the first p-type nitride semiconductor layer and the active layer.
5 . The nitride semiconductor device of claim 4 , wherein the non-doped nitride semiconductor layer has a smaller band gap than a band gap of the second p-type nitride semiconductor layer.
6 . The nitride semiconductor device of claim 5 , wherein the non-doped nitride semiconductor layer has a band gap equal to the band gap of the first p-type nitride semiconductor layer.
7 . The nitride semiconductor device of claim 4 , wherein a total thickness of the non-doped nitride semiconductor layer and the first p-type nitride semiconductor layer is no less than 1 nm and no more than 50 nm.
8 . The nitride semiconductor device of claim 7 , wherein the second p-type nitride semiconductor layer has a thickness of no less than 5 nm and no more than 20 nm.
9 . The nitride semiconductor device of claim 8 , wherein a region of the second p-type nitride semiconductor layer which has an Mg concentration of 8×10 18 cm −3 or less has a thickness of 1 nm or less.
10 . The nitride semiconductor device of claim 1 , wherein,
the p-type nitride semiconductor layer further includes a third p-type nitride semiconductor layer having a smaller band gap than a band gap of the second p-type nitride semiconductor layer; and
the second p-type nitride semiconductor layer is located between the third p-type nitride semiconductor layer and the first p-type nitride semiconductor layer.
11 . The nitride semiconductor device of claim 10 , wherein the third p-type nitride semiconductor layer has a smaller band gap than the band gap of the first p-type nitride semiconductor layer.
12 . The nitride semiconductor device of claim 10 , wherein the third p-type nitride semiconductor layer functions as a cladding layer.
13 . The nitride semiconductor device of claim 10 , wherein at least one of the first p-type nitride semiconductor layer and the second p-type nitride semiconductor layer contains In.
14 . The nitride semiconductor device of claim 13 , wherein the second p-type nitride semiconductor layer has a greater In mole fraction than an In mole fraction of the first p-type nitride semiconductor layer.
15 . A production method for a nitride semiconductor device including a p-type nitride semiconductor layer, an n-type nitride semiconductor layer, and an active layer interposed between the p-type nitride semiconductor layer and the n-type nitride semiconductor layer, wherein: the p-type nitride semiconductor layer includes a first p-type nitride semiconductor layer containing Al and Mg and a second p-type nitride semiconductor layer containing Mg; the first p-type nitride semiconductor layer is located between the active layer and the second p-type nitride semiconductor layer; and the second p-type nitride semiconductor layer has a greater band gap than a band gap of the first p-type nitride semiconductor layer, the production method comprising:
a step of forming the n-type nitride semiconductor layer;
a step of forming the active layer;
a step of forming the first p-type nitride semiconductor layer containing Al and Mg by supplying both a source gas having Mg and a source gas having Al; and
a step of forming the second p-type nitride semiconductor layer by supplying a source gas having Mg.
16 . The production method of claim 15 , further comprising, before the step of forming the first p-type nitride semiconductor layer, a step of forming a non-doped nitride semiconductor layer which contains Al by supplying a source gas having Al without supplying any p-type impurities.
17 . The production method of claim 15 , wherein,
the first p-type nitride semiconductor layer has an Al concentration of no less than 1×10 20 cm −3 and no more than 2×10 21 cm −3 ; and
a region of the first p-type nitride semiconductor layer in which the Al concentration is no less than 1×10 20 cm −3 and no more than 2×10 21 cm −3 has a thickness of 1 nm or more.