Research on Blue Semiconductor Lasers Based on MOCVD

为了实现高密度数据存储和全彩色显示，对蓝色半导体激光器的实现提出了很高的要求。为此，II-VI半导体和GaN基宽禁带半导体得到了积极的研究。该项目的实施为实现基于II-VI半导体的这种蓝光激光器奠定了基础。MOCVD是大规模生产光学器件的关键技术，但锌硒异质结中的p型掺杂仍然是一个严重的问题。我们用两性本征缺陷模型分析了掺杂问题，并对已报道的测量结果给予了合理的解释。从这一结果中我们发现，生长温度可能是实现更高p型掺杂的关键因素之一，这也与已有的不同生长方法的报道一致。我们还提出了一种新的掺杂方法，这种掺杂方法是基于周期性的亚单层掺杂，在锌硒中可以实现净受主浓度大于1×10^&lt；18&gt；cm^&lt；-3&gt；尽管ZnTe与ZnSe严重失配，可能会产生失配位错，但类似的在ZnSe中掺杂GaAs：Zn的方案对解决这一问题也是有效的。通过这些结果，II-VI蓝色半导体激光器MOCVD生长中的掺杂问题将被解决。增加II-VI异质结中的能带偏移量是防止激光器漏电流的另一个关键问题。为此，我们提出了使用短周期的MgS/ZnSe超晶格，并通过光致发光和XPS测量证明了其高势垒高度。此外，还展示了自组织网点的形成，这将降低激光操作的阈值电流。这些丰硕的成果结合在一起，有望实现高性能的蓝光半导体激光器。

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.