Research on Blue Semiconductor Lasers Based on MOCVD

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Realization of blue semiconductor lasers is highly requested for high-density data storage and for full-color displays. II-VI semiconductors and GaN-based widegap semiconductors are actively studied for this purpose. This project was performed to establish the basis for realizing such blue lasers based on the II-VI semiconductors. MOCVD is the key technology for mass production of optical devices, but the p-type doping in ZnSe based heterostructures is the remaining serious problem. We have analyzed the doping problem with an amphoteric native defect model and could give reasonable interpretation to the reported measurements. From this result, we found the growth temperature can be one of the key factor for realizing higher p-type doping, which is also consistent with the existing reports with different growth methods. We also demonstrated a new doping method based on the periodic submonolayr insertion of ZnTe : Li, and the net acceptor concentration above 1x10^<18>cm^<-3> could be realized in ZnSe. Although ZnTe is highly mismatched to ZnSe and misfit dislocations may be induced, the similar scheme of doping GaAs : Zn in ZnSe is also effective for this problem. From these results, the doping issue for the MOCVD growth of II-VI blue semiconductor lasers will be cleared.Increase of the band offset in II-VI heterostructures is another key issue to prevent leakage currents in laser diodes. For this purpose, we proposed the use of short period MgS/ZnSe superlattices and demonstrated the high barrier height with photoluminescence and XPS measurements. Self-organized dot formation was also demonstrated, which will reduce the threshold current for the laser operations. By the combination of these fruitful results in this project, realization of high-performance blue semiconductor lasers can be expected.