| Research Abstract |
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.
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