Semiconductor device
A semiconductor device has an active layer, a first semiconductor layer of first conductive type, an overflow prevention layer disposed between the active layer and the first semiconductor layer, which is doped with impurities of first conductive type and which prevents overflow of electrons or holes, a second semiconductor layer of first conductive type disposed at least one of between the active layer and the overflow prevention layer and between the overflow prevention layer and the first semiconductor layer, and an impurity diffusion prevention layer disposed between the first semiconductor layer and the active layer, which has a band gap smaller than those of the overflow prevention layer, the first semiconductor layer and the second semiconductor layer and which prevents diffusion of impurities of first conductive type.
1. A semiconductor device, comprising
an active layer which comprises a single or multiple quantum well structure having a quantum well having In x1 Ga 1-x1 N (0<x≦1) and a barrier layer having In x2 Ga 1-x2 N (0≦x2<1, x1>x2);
a first semiconductor layer which comprises p-type GaN-based compound semiconductor;
a first layer having In 1-x-y1 Ga x Al y1 N (0≦x<1, 0<y1≦1), disposed between the active layer and the first semiconductor layer;
a second semiconductor layer which comprises p-type GaN-based compound semiconductor, which is disposed either between the active layer and the first layer or between the first layer and the first semiconductor layer; and
a second layer having In y2 Ga 1-y2 N (0<y2≦1), disposed between the first semiconductor layer and the active layer,
a band gap of the second layer being smaller than those of the first layer, the first semiconductor layer and the second semiconductor layer,
a lattice constant of the second layer being larger than those of the first layer, the first semiconductor layer and the second semiconductor layer,
the thickness of the second semiconductor being from 1 nm to 15 nm, and
the second layer being doped with Mg from 1×10 17 cm −3 to 1×10 19 cm −3 ,
wherein an In composition ratio of the second layer is higher than those of the first layer, the first semiconductor layer and the second semiconductor layer.
2. The semiconductor device according to claim 1 ,
wherein the active layer emits a light with a predetermined wavelength;
the first semiconductor layer is used as a p-type clad layer; and
the second semiconductor layer is used as a p-type guide layer.
3. The semiconductor device according to claim 2 , further comprising:
an n-type guide layer disposed on a side of the active layer opposite from the p-type guide layer, which comprises GaN or In x3 Ga 1-x3 N (0<x3<1).
4. The semiconductor device according to claim 1 ,
wherein the first layer contains In and comprises In 1-x-y1 Ga x Al y1 N (0≦x<1, 0<y1<1).
5. The semiconductor device according to claim 1 ,
wherein the second semiconductor layer is disposed between the active layer and the first layer; and
the second layer is disposed between the second semiconductor layer and the first layer.
6. The semiconductor device according to claim 1 ,
wherein an In composition ratio of the second layer from 2% to 10%.
7. The semiconductor device according to claim 1 ,
wherein an In composition ratio of the second layer from 3% to 8%.
8. The semiconductor device according to claim 1 ,
wherein an In composition ratio of the first layer 2% or less.
9. The semiconductor device according to claim 1 ,
wherein the thickness of the second semiconductor being from 1 nm to 10 nm.
10. The semiconductor device according to claim 1 ,
the first layer being doped with Mg from 4×10 18 cm −3 to 5×10 19 cm −3 .