| Research Abstract |
"Opto-Electronic Integrated Circuit (OEIC)" is a key device in future information and communications society. Besides electronic signal processing, it makes full use of optoelectronics information processing technology. In order to realize the OEIC, hetero-epitaxial technology is important. For example, dislocation free layer is essential to realize a long lifetime laser as light source. However, dislocation density of GaAs grown on Si is an order of 10^6 cm^<-2> now and is still too high.
In order to overcome the above problems and to grow dislocation free crystals, we proposed "microchannel epitaxy (MCE)". In MCE, the information of crystal of substrate is transmitted through the narrow window ("microchannel"), but the information of defects in the substrate is cut off, and reduction of dislocation density can be realized. In this research subject, we grew dislocation free GaAs epitaxial layer on Si substrate and tried to fabricate Vertical Cavity Surface Emitting Laser (VCSEL). Through this research, the following outcome was rewarded.
1. A high-performance laser with gain-guided structure was realized on Si substrate. Though the laser was operated only by a pulsed current, the performance of the laser was found no less inferior than that of the laser fabricated on GaAs substrate.
2. Incorporation mechanism of oxygen into AlGaAs layers was investigated, because reduction of oxygen impurity is mandatory for the improvement of laser characteristics.
3. The performance of the laser was found strongly related to the concentration of oxygen, and it was experimentally confirmed that reduction of oxygen concentration is essential to decrease the threshold current density.
4. VCSEL with oxide-confinement structure was fabricated on GaAs substrate and it showed a high-grade performance of laser operation.
5. "Oxide block effect" was also tried to utilize in order to improve the flexibility of VCSEL processing.
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