Xd. Xiao et al., INTERFACES OF STRAINED-LAYER (GENSIM)(P) SUPERLATTICES STUDIED BY 2ND-HARMONIC GENERATION, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 15(4), 1997, pp. 1112-1116
Second-harmonic (SH) generation has been applied to study the interfac
es of short-period (GenSim)(p) strained layer superlattices. From the
SH signal and its symmetry, we have concluded that (i) over an area of
optical wavelength size, the superlattices were grown with nonuniform
layer thickness in each period; (ii) along the growth direction, the
atomic structure of Si-on-Ge and Ge-on-Si interfaces are not symmetric
; and () a structural change of the interfaces, possibly from ni the i
ncrease of misfit dislocation or other defect density, occurs when the
thickness of the strained Ge layer in each period exceeds about six l
ayers. The SH spectroscopic results showed defects contributed dominan
tly for (Ge7Si8)(4), but substantial contribution from Si-Ge bonds for
(Ge4Si4)(3) and (Ge5Si5)(3) still exists. (C) 1997 American Vacuum Soc
iety.