F. Jackson et al., ROTATION ANISOTROPY BY 2ND-HARMONIC GENERATION OF II-VI EPILAYERS ON A GAAS[100] SUBSTRATE - BARE CMT AND CDS ON CMT, Journal of the Chemical Society. Faraday transactions, 92(20), 1996, pp. 4061-4067
Citations number
38
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
Using second harmonic generation (SHG), the rotation anisotropy for ca
dmium mercury telluride, CdxHg1-xTe (CMT) epilayer surfaces grown on a
GaAs [100] substrate has been observed. For the bare CMT {100} surfac
e, four peaks were obtained, in agreement with similar studies on comp
ounds with the zinc-blende crystal structure. It is shown that the ove
rall SH response arises from an interference pattern between the bulk
and the surface contributions. From the interference patterns observed
in the different polarisation configurations, it is concluded that th
e CMT epilayer has grown following the vicinal surface of the GaAs (10
0) substrate. These vicinal surfaces are also responsible for the pref
erential symmetry exhibited by the surface. When a layer of oxide is e
lectrochemically grown onto the CMT layer, the SH response essentially
retains the underlying CMT symmetry although changes in the peak inte
nsities were noted. These changes can arise from a modified interferen
ce pattern between the bulk and surface contributions as compared with
that of the bare CMT surface. Finally, we have studied the SH respons
e from an anodically grown CdS film on the CMT substrate. A large enha
ncement in the SH intensity was found, resulting from the non-linear-a
ctive CdS layer. It is shown that this layer has grown with the cubic
close packing structure of the underlying CMT substrate, its anisotrop
ic response being similar to that of the bare CMT. It is also observed
that in this case, the interference pattern is much less pronounced,
indicating a much weaker surface contribution. This study therefore in
dicates that SHG is a valuable technique for following the in situ gro
wth of non-linear-active films used in passivating the CMT epilayers.