| 摘要 |
PURPOSE:To obtain a quantum well structure semiconductor laser capable of making a laser beam oscillate in a short wavelength and at a low thrshole value even in case the quantum well layer is made very thinner by a method wherein graded layers are provided on both sides of the quantum well layer. CONSTITUTION:This quantum well structure semiconductor laser having at least one quantum well layer 4 or more in its main luminous region is constituted into a structure, wherein a first graded layer 3 and a second graded layer 5 are provided on both sides of the quantum well layer 4, the forbidden band width thereof becomes smaller gradually as the graded layers 3 and 5 get nearer the quantum well layer 4 in the film thickness direction of the graded layers and the thicknesses of the graded layers are formed into about 5 Angstrom or more to 300Angstrom or less. As there exist the first graded layer 3 and the second graded layer 5 on both sides of the quantum well layer 4, the thickness of the equivalent quantum well layer is formed thicker. As a result, even though carriers to pass through the quantum well layer are generated, the carriers are captured by these graded layers and are immediately pulled back by the internal electric field in the graded layers. Accordingly, even when the thickness of the quantum well layer is made very thinner, the injection efficiency does not worsen because the carriers are captured by these graded layers.
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