Semiconductor laser, semiconductor device and nitride series...

Details Semiconductor laser, semiconductor device and nitride series... Semiconductor laser, semiconductor device and nitride series...

2001-06-05

2004-12-28

Wong, Don (Department: 2828)

Coherent light generators

Particular active media

Semiconductor

C372S043010, C372S044010, C372S046012, C372S049010, C372S049010, C372S049010, C372S050121

Reexamination Certificate

active

06836498

ABSTRACT:

RELATED APPLICATION DATA
The present application claims priority to Japanese Applications Nos. P2000-168312 filed Jun. 5, 2000, and P2000-260722 filed Aug. 30, 2000, which applications are incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns a semiconductor device having a seed crystal layer and a crystal growth layer grown on the basis of the seed crystal layer, a semiconductor laser and a nitride series III-V group compound substrate, as well as a manufacturing method thereof.
This invention also relates to a semiconductor laser and a semiconductor device having a substrate comprising a nitride series III-V group compound and a semiconductor layer comprising a nitride series III-V group compound grown on the basis of the substrate as well as a manufacturing method thereof.
2. Description of the Related Art
Nitride series III-V group compound semiconductors such as GaN, AlGaN mixed crystals or GaInN mixed crystals are direct transition semiconductor materials and have a feature in which the forbidden band gap ranges from 1.9 eV to 6.2 eV. Accordingly, the nitride series III-V group compound semiconductors can provide emission from a visible region to a ultraviolet region and have been noted as materials constituting semiconductor light emitting devices such as semiconductor lasers (laser diodes: LD) or light emitting diode (LED). Further, the nitride series III-V group compound semiconductors have also been noted as materials constituting electronic devices since they show high saturation electron velocity and breakdown electric field.
The semiconductor devices described above are generally produced by growing a nitride series III-V group compound semiconductor layer using a vapor deposition method on a substrate for growing comprising, for example, sapphire (&agr;-Al
2
O
3
) or silicon carbide (SiC). However, since lattice mismatching or difference of heat expansion coefficient is large between sapphire or silicon carbide and the nitride series III-V group compound semiconductor, lattice defects such as dislocations are formed for moderating strains in the nitride series III-V group compound semiconductor layer. When the lattice defects are formed, the defects form centers of non-light emissive recombination which do not emit light even when electrons and holes are recombined or current leak portions, to deteriorate optical or electrical characteristics of the semiconductor device.
In view of the above, a method of decreasing the penetrative dislocation density, for example, by utilizing selective growing technique has been proposed in recent years. This method is adapted to selectively etch a nitride series III-V group compound semiconductor layer grown on a substrate for growing to form a seed crystal layer and grow a crystal growth layer laterally from the side wall surface of the seed crystal layer.
Further, it has also been studied to use a substrate comprising a nitride series III-V group compound. The substrate comprising the nitride series III-V group compound is prepared by growing on a substrate for growing comprising, for example, sapphire and then separation from the substrate for growing. Since the use of the substrate comprising the nitride series III-V group compound can overcome the problems described above and obtain excellent heat conductivity compared with the sapphire substrate, it has an advantage capable of effectively dissipating heat generated during driving. Further, since an electrode can be disposed to the rear face of the substrate by adding an impurity to provide conductivity, the surface area of the device can be decreased to provide a merit of high density mounting.
However, the first method involves a problem that defects are increased by the dislocation generated in the crystal growth layer if there is fluctuation of the crystallographic axes in the crystal growth layer. Further, it has a problem that the dislocation tends to propagate while extending in the lateral direction. Accordingly, for improving device characteristics, it has been desired to grow a crystal growth layer with less fluctuation of the crystallographic axes.
Further, the second method involves a problem that the dislocation density is as high as about 1×10
8
cm
−2
to 1×10
11
cm
−2
since the substrate comprising the nitride series III-V group compound is prepared, for example, by growing on a substrate comprising sapphire or the like. Accordingly, the dislocation density also increases in the layer of the nitride series III-V group compound semiconductor to be grown on the substrate, failing to improve the device characteristics.
The problems described above also appear in a case of growing a nitride series III-V group compound substrate on the substrate for growing and it is indispensable to grow a crystal growth layer with less fluctuation of the crystallographic axes also for obtaining a nitride series III-V group compound substrate of good quality.
SUMMARY OF THE INVENTION
This invention has been accomplished in view of the foregoing problems and intends to provide a semiconductor laser, a semiconductor device and a nitride series III-V group compound substrate capable of obtaining a crystal growth layer with less fluctuation of the crystallographic axes and capable of improving the device characteristics, as well as a manufacturing method therefor.
This invention also intends to provide a semiconductor laser and a semiconductor device capable of decreasing the dislocation density and improving the device characteristics, as well as a manufacturing methods therefor.
A semiconductor laser according to this invention comprises a plurality of spaced apart seed crystal layers comprising a nitride series III-V group compound semiconductor and a crystal growth layer comprising a nitride series III-V group compound semiconductor which is grown on the basis of the seed crystal layer wherein
the seed crystal layer is adapted in that product of a width (unit: &mgr;m) at a boundary relative to the crystal growth layer along the arranging direction and a thickness (unit &mgr;m) in the laminating direction of the crystal growth layer is 15 or less.
Another semiconductor laser according to this invention comprises band-like seed crystal layers comprising a nitride series III-V group compound semiconductor and a crystal growth layer comprising a nitride series III-V group compound semiconductor which is grown on the basis of the seed crystal layer wherein
the seed crystal layer is adapted in that a product of a width (unit: &mgr;m) at a boundary relative to the crystal growth layer along the direction perpendicular to the extending direction and a thickness (unit &mgr;m) in the laminating direction of the crystal growth layer is 15 or less.
A semiconductor device according to this invention comprises a plurality of spaced apart seed crystal layers comprising a nitride series III-V group compound semiconductor and a crystal growth layer comprising a nitride series III-V group compound semiconductor which is grown on the basis of the seed crystal layer wherein
the seed crystal layer is adapted in that product of a width (unit: &mgr;m) at a boundary relative to the crystal growth layer along the arranging direction and a thickness (unit &mgr;m) in the laminating direction of the crystal growth layer is 15 or less.
Another semiconductor device according to this invention comprises band-like seed crystal layers comprising a nitride series III-V group compound semiconductor and a crystal growth layer comprising a nitride series III-V group compound semiconductor which is grown on the basis of the seed crystal layer wherein
the seed crystal layer is adapted in that a product of a width (unit: &mgr;m) at a boundary relative to the crystal growth layer along the direction perpendicular to the extending direction and a thickness (unit &mgr;m) in the laminating direction of the crystal growth layer is 15 or less.
A nitride series III-V group compound substrate according to this

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