Growth and Properties of (III-V)-(II-VI) Super Lattices by Photo-Assisted Atomic Layer Epitaxy

由III-V复合势垒和II-VI复合势垒组成的新型应变层超晶格有望成为工作在可见光区的新型光电子器件材料。制备SLS的难点之一是GaAs层和ZnSe层的外延温度不同。此外，尽管在250-350℃的低温下在GaAs上生长ZnSe是相当容易的，但在这样的温度下在ZnSe上生长GaSe是相当困难的，因为As在ZnSe上的附着系数很小。因此，降低外延温度，尤其是降低外延温度对制备GaAsZnSe半导体激光器是非常重要的。(1)用MOVPE和MOMBE方法在GaAs上实现了ZnSe和ZnS的原子层外延。(2)用Ar离子激光谱线照射生长表面，可以显著降低GaSe上的外延温度，这归因于在ZnSe表面上的光催化反应。(3)还发现光照射对降低GaSe上的外延温度非常有效。(4)利用表面光吸收(SPA)和反射差分光谱(RDS)建立了对GaAs层和ZnSe层外延的在线监测技术。(5)从理论上计算了GaAsZnSe SLS的光学性质，并对SLS结构进行了优化。在此基础上，对GaAsZnSe SLS的制备和表征进行了研究。

A new type of strained layer superlattices (SLSs) consisting of III-V compound wells(GaAs)and II-VI compound barriers(ZnSe)are expected as materials for new optoelectronic devices operating in visible region. One of the difficulties when fabricating the SLSs is the difference in epitaxy temperatures for GaAs and ZnSe. Further, although it is fairly easy to grow ZnSe on GaAs at such low temperatures as 250 - 350 C, it is quite difficult to grow GaAs on ZnSe at such temperatures, because the sticking coefficient of As on ZnSe is quite small. Therefore, lowering the epitaxy temperature, especially for GaAs, is very important to fabricate the GaAs-ZnSe SLSs. This is also effective to suppress the cross diffusion between GaAs and ZnSe and also to obtain atomically controlled sharp interfaces between them.(1) Atomic layer epitaxy of ZnSe and ZnS on GaAs has been achieved by MOVPE and MOMBE.(2) It has been shown that the epitaxy temperature for ZnSe on GaAs can be drastically lowered by irradiating the growing surface with Ar ion laser lines, and this has been attributed to the photocatalytic reaction on the ZnSe surface.(3) It has also been found that photoirradiation is very effective to lower the epitaxy temperature for GaAs on ZnSe, which is also attributed to the photocatalysis on ZnSe.(4) In-situ monitoring technique has been developed for epitaxy of GaAs and ZnSe layers utilizing surface photoabsorption (SPA) and reflectance-difference spectroscopy (RDS).(5) Optical properties of GaAs-ZnSe SLSs have been theoretically calculated and optimization for the SLS structures has been done.On the basis of these results, fabrication and characterization of GaAs-ZnSe SLSs are under investigation now.