Long-wavelength semiconductor light emitting device and its manufacturing method

DETAILED DESCRIPTION It is therefore an object of the present invention to provide a long-wavelength semiconductor light emitting device having excellent characteristics and a long lifetime, as well as its manufacturing method, with which an active layer of a good quality can be obtained because of a sufficiently low concentration of Al impurity in the active layer.
The Inventors made vigorous researches to accomplish the above-mentioned object as abstracted below.
As a technique for solving the problems in the prior techniques, the Inventors have found that the concentration of Al impurity contained in the active layer can be reduced to 1×1019 cm-3 if the supply of the source material of a group III element is interrupted during the growth of a layer (such as an optical guide layer) anteriorly adjacent to the active layer of a GaInNAs long-wavelength semiconductor light emitting device or immediately before the start of growth of the active layer, and a highly reactive gas such as DMHy is supplied together with a source material of As used as a group V element.
The Inventors also found that the Al impurity concentration reduced to this level ensures characteristics acceptable for practical use.
This technique is completely different from techniques of Patent Literature 1 and Non-patent Literatures 2 and 3.
FIG.
1 shows correlation between the peak concentration of Al impurity in the GaInNAs active layer obtained by bar check and the slope efficiency.
FIG.
2 shows correlation between the characteristic temperature measured after assembly of the laser and the peak concentration of Al impurity in the GaInNAs active layer.
FIG.
3 shows correlation the emission intensity (peak intensity) from the GaInNAs active layer obtained by photoluminescence (PL) measurement and the peak concentration of Al impurity in the GaInNAs active layer.
Note that the reflectance of the front edge of the laser is 50% and the reflectance of the rear edge is 95%.
It is appreciated from FIGS.
1, 2 and 3 that, under the Al impurity concentration equal to or lower than 1×1019 cm-3, the slope efficiency is approximately equal to or higher than 0