| 摘要 |
PURPOSE:To obtain a variable wavelength DBR laser with a reduced loss by a method wherein the forbidden band width of a quantum well is controlled by varying the surface passivation conditions and the equivalent wavelength of the forbidden band width is shorter in the wavelength control region of the layer structure of the laser than in the light emitting region and the emitted light wavelength is made to coincide with the wavelength at which the electro- optical coefficient of the wavelength control region has the maximum value. CONSTITUTION:An n-type Al0.4Ga0.6As cladding layer 2, an MQW active layer 3, a p-type Al0.1Ga0.9As waveguide layer 4, a p-type Al0.4Ga0.6As cladding layer 5 and a p-type GaAs contact layer 6 are successively built up on an n<+>type GaAs substrate 1 by MBE to form a layer structure. The layer structure is divided into two regions I and II. An SiO2 layer 11 with a thickness of 2000 Angstrom is formed on the region II as a passivation film. Then the layer structure is subjected to a heat treatment in a sealed tube under an arsenic pressure of 100Torr and a temperature of 850 deg.C for 40 minutes. As a result, the passivation effect given by the arsenic pressure functions remarkably in the region I to which the arsenic pressure is directly applied and PL of the MQW is maintained at about 820nm. On the other hand, PL of the MQW is shifted to about 805nm by the heat treatment in the region II under the passivation film. In other words, the forbidden band widths E1 and E2 of the regions I and II become 820nm and 805nm in wavelength equivalent respectively. |
