Yu Ming-Ren

The elimination of in islands on InP surfaces and ITS mechanism

The surface indium islands originated by argon ion bombardment can be removed by evaporating phosphorous on InP surface followed by annealing. A possible mechanism of elimination of In islands is proposed based on the experimental ELS and XPS data.

Order alloy in GexSi1-x/Si(100) strained-layer superlattices

The GexSi1-x/Si(100) strained-layer superlattices have been investigated by means of the transmission electron microscopy of the cross-sectional specimen (XTEM) and the high resolution electron microscopy (HREM). The order alloy with a period of modulation twice as large as the lattice constant along 100 zone axis has been found in the alloy layers of the superlattices with x≈0.4-0.5. This order structure makes the superlattices inhomogeneously strained. The result of the computer simulation shows that the order alloy exhibits an altermating stack of 2 monolayers of Ge atoms and 2 monolayers of Si atoms along the 100 zone axis. The calculated elastic strain energy of the disorder alloy reported in the literature is very close to that of the order alloy along 100 zone axis. Thus, during the MBE growth of the alloy layers, both the disorder and order alloys can be formed along 100 zone axis.

Determination of Photoelastic Constant Ratio of the Two Components in GexSi1-x/Si Superlattice

From the intensity ratio of the folded longitudinal acoustic phonons with respect to the longitudinal acoustic phonon in a Ge0.51 Si0.49/Si superlattice (SL), we obtained a photoelastic constant ratio of 6.6 for Ge0.51 Si0.49 alloy with respect to Si in the SL at wavelength 5145 A, which is 2.6 times greater than that obtained by [He Phys. Rev. B 39 (1989) 5919] in a Ge0.5 Si0.5/Si SL.

Raman scattering intensities of folded longitudinal acoustic phonons in GexSi1-x / Si superlattices

In terms of photoelastic mechanism we have investigated the Raman scattering intensities of the folded longitudinal acoustic (FLA) phonons in GexSi1-x/Si superlattices (SLs), taking into account the differences between the acoustic and photoelastic parameters of the two constituents in the SLs. The relative intensities calculated for the FLA phonons are in excellent agreement with the experimental results at the frequencies up to about 50 cm-1. The broadening of the linewidth arising from the so called strong acoustic attenuation, which was reported previously located around the frequency 15 cm-1 in GexSi1-x/Si SLs (x ≈ 0.5), has not been observed in this work.