The bandgaps of semiconductors are decreased with increasing temperature which leads to the red-shift lasing wavelength of semiconductor lasers. Therefore, how to stabilize the lasing wavelength under different working temperatures becomes an important issue. The composition and size variation of quantum dots are additional factors which affect the lasing wavelength shift. It is well known that diffusion speeds up with increasing temperature and causes the wavelength shift to occur. To avoid the change of composition and size of quantum dots during growth, the suppression of the diffusion process is necessary to ensure the quantum dots to have a well preserved initial stage.
The laser active region with InAs/GaAsN digital alloy quantum well structure was grown by molecular beam epitaxy in this experiment. The self-assembled quantum dots formed in the digital alloy quantum well under high stress. The carriers congregated in the lower energy levels with broadening distribution of composition and size of quantum dots. The peak wavelength shifted toward a longer wavelength with decreasing temperature. The behavior was contrary to the Varshni equation with shrinking bangaps under increasing temperature. Therefore, the sensitivity of the wavelength with temperature decreased. The size distribution of InAs quantum dots on the gradient quantum well broadened under higher arsenic pressure. Consequently, the wavelength sensitivity of quantum dots with temperature decreased. Finally, the InAs quantum dots were capped with the InAlAs quantum well to avoid the diffusion during high temperature growth. The capped InAs quantum dots prevented the wavelength shift from the composition and size variation of quantum dots.
For the reason of stabilizing the lasing wavelength of the long wavelength semiconductor laser in optical communication system, it becomes an important topic to create new materials for the active region of the laser structure to avoid the lasing wavelength shift. The next generation temperature insensitive laser devices will be produced with the method which was created in this experiment.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0910106-190919 |
| Date | 10 September 2006 |
| Creators | Chen, Liang-pin |
| Contributors | K.-y. Hsieh, New-jin Ho, Der-shin Gan, Ikai Lo, Jui-hung Hsu, D.-r. Hang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0910106-190919 |
| Rights | not_available, Copyright information available at source archive |
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