Semiconductor laser

DETAILED DESCRIPTION One object of the present invention is to provide a semiconductor laser having a higher efficiency and a lower threshold current than conventional semiconductor lasers.
In order to accomplish the object described above, the semiconductor laser in accordance with the present invention localizes electrons and holes or excitons formed by a combination of them not only in the current flowing direction in the same way as in the prior art semiconductor lasers but also in a plane perpendicular to the current flowing direction.
In order to localize the electrons, the holes and the excitons in the plane perpendicular to the current flowing direction as described above, the present invention forms a spatial fluctuation of potential so that potential differs from position to position inside the plane described above.
The semiconductor laser of the present invention obtains the spatial fluctuation of the potential by making an intentionally incomplete periodicity of the atomic arrangement of a crystal inside the plane perpendicular to the current flowing direction.
More definitely, corrugations or ruggedness (hereinafter referred to as ruggedness) whose level difference is from 1/10 to 1/2 of the mean thickness of the active layer and which has a mean pitch, between projected portions, of up to 100 nm are disposed on the surface of the active layer.
The lower limit of the mean pitch is about 10 nm from the restriction imposed on the processing technique, but it may be a smaller pitch, in principle.
In other words, a theoretically perferred mean pitch of the ruggedness is about the spread of the wave function of the electron.
In the case of GaAs, for example, the spread of the wave function is about 10 nm.
Therefore, the mean pitch which has been believed considerably more effective than conventionally, though it may not be optimal, includes a range smaller than 10 nm.
If the mean pitch of the ruggedness exceeds 100 nm, the effect of the present invention will be lost undesirably