Nitride-based semiconductor laser device
A nitride-based semiconductor laser device capable of elongating the life thereof is obtained. This nitride-based semiconductor laser device comprises a first cladding layer consisting of a first conductivity type nitride-based semiconductor, an emission layer, formed on the first cladding layer, consisting of a nitride-based semiconductor and a second cladding layer, formed on the emission layer, consisting of a second conductivity type nitride-based semiconductor, while the emission layer includes an active layer emitting light, a light guiding layer for confining light and a carrier blocking layer, arranged between the active layer and the light guiding layer, having a larger band gap than the light guiding layer.
1. A nitride-based semiconductor laser device comprising:
a first cladding layer consisting of a first conductivity type nitride-based semniconductor;
an emission layer, formed on said first cladding layer, consisting of a nitride-based semiconductor; and
a second cladding layer formed on said emission layer, consisting of a second conductivity type nitride-based semiconductor, wherein
said emission layer includes:
an active layer emitting light,
a light guiding layer for confining light; and
a carrier blocking layer, arranged between said active layer and said light guiding layer, having a larger band gap than said light guiding layer,
the nitride-based semiconductor laser device further comprising a light spreading layer, arranged at least either between said emission layer and said first cladding layer or between said emission layer and said second cladding layer, having a smaller refractive index and a larger band gap than adjacent said first or second cladding layer.
2. The nitride-based semiconductor laser device according to claim 1 , wherein
said light guiding layers are formed on the upper and lower surfaces of said active layer respectively, and
said carrier blocking layers are arranged both between said active layer and said light guiding layer formed on the upper surface of said active layer and between said active layer and said light guiding layer formed on the lower surface of said active layer.
3. The nitride-based semiconductor laser device according to claim 1 , wherein
said light spreading layers are arranged both between said emission layer and said first cladding layer and between said emission layer and said second cladding layer.
4. The nitride-based semiconductor laser device according to claim 1 , wherein
at least either said carrier blocking layer or said light spreading layer contains one or two elements selected from a group consisting of B, Al, In, Ga and Tl.
5. The nitride-based semiconductor laser device according to claim 1 , wherein
at least either said first cladding layer or said second cladding layer consists of a nitride containing Al, Ga and In.
6. The nitride-based semiconductor laser device according to claim 5 , further comprising a light spreading layer, arranged at least either between said emission layer and said first cladding layer or between said emission layer and said second cladding layer, having a smaller refractive index and a larger band gap than adjacent said first or second cladding layer, wherein
at least either said carrier blocking layer or said light spreading layer consists of a nitride containing Al, Ga and In.
7. The nitride-based semiconductor laser device according to claim 5 , wherein
at least either said first cladding layer or said second cladding layer consists of a nitride, containing Al, Ga and In, having a lattice constant substantially identical to that of GaN.
8. The nitride-based semiconductor laser device according to claim 1 , wherein
said carrier blocking layer consists of a nitride containing Al, Ga and In.
9. The nitride-based semiconductor laser device according to claim 1 , wherein
said emission layer includes an active layer consisting of either a single quantum well structure or a multiple quantum well structure.
10. The nitride-based semiconductor laser device according to claim 1 , wherein
said first cladding layer consisting of said first conductivity type nitride-based semiconductor is formed on a first conductivity type nitride-based semiconductor substrate.
11. The nitride-based semiconductor laser device according to claim 1 , wherein
a vertical beam divergence angle is not more than 20°.
12. A nitride-based semiconductor laser device comprising:
a first cladding layer consisting of a first conductivity type nitride-based semiconductor;
an emission layer, formed on said first cladding layer, consisting of a nitride-based semiconductor; and
a second cladding layer, formed on said emission layer, consisting of a second conductivity type nitride-based semiconductor, wherein
said emission layer includes:
an active layer emitting light, and
a light guiding layer formed on at least either the upper surface or the lower surface of said active layer for confining light,
said nitride-based semiconductor laser device further comprising a light spreading layer, arranged between said light guiding layer and either said first or second cladding layer being formed on the same side of said light guiding layer, having a smaller refractive index and a larger band gap than said either first or second cladding layer being formed on the same side of said light guiding layer.
13. The nitride-based semiconductor laser device according to claim 12 , further including light guiding layers for confining light on both of the upper and lower surfaces of said active layer.
14. The nitride-based semiconductor laser device according to claim 12 , further comprising another light spreading layer arranged between said active layer and either said second or first cladding layer being formed on the opposite side of said light guiding layer, having a smaller refractive index and a larger band gap than said either second or first cladding layer being formed on the opposite side of said light guiding layer.
15. The nitride-based semiconductor laser device according to claim 14 , further including a carrier blocking layer, arranged between said active layer and said light guiding layer, having a larger band gap than said light guiding layer.
16. The nitride-based semiconductor laser device according to claim 15 , wherein
at least either said carrier blocking layer or said light spreading layer contains one or two elements selected from a group consisting of B, Al, In, Ga and Tl.
17. The nitride-based semiconductor laser device according to claim 12 , wherein
at least either said first cladding layer or said second cladding layer consists of a nitride containing Al, Ga and In.
18. The nitride-based semiconductor laser device according to claim 17 , wherein
at least either said first cladding layer or said second cladding layer consists of a nitride, containing Al, Ga and In, having a lattice constant substantially identical to that of GaN.
19. The nitride-based semiconductor laser device according to claim 13 , wherein
said light spreading layer consists of a nitride containing Al, Ga and In.
20. The nitride-based semiconductor laser device according to claim 12 , wherein
said emission layer includes an active layer consisting of either a single quantum well structure or a multiple quantum well structure.
21. The nitride-based semiconductor laser device according to claim 12 , wherein
said first cladding layer consisting of said first conductivity type nitride-based semiconductor is formed on a first conductivity type nitride-based semiconductor substrate.
22. The nitride-based semiconductor laser device according to claim 12 , wherein
a vertical beam divergence angle is not more than 20°.