Dielectric function spectra of strained and relaxed Si1−xGex alloys (x=0–0.25)

Abstract

Dielectric function spectra for strained and relaxed Si1−xGex alloys with x∼0.13 and 0.20 are presented in numerical form. The effect of strain is shown to cause a modification of the spectra in the E1 critical point region, resulting in a decrease in refractive index at 1.96 eV, amounting to 0.06 at x=0.22. The spectral dependence of the refractive index is presented for a series of strained layers. An overview is given of spectral databases and the single-wavelength ellipsometry data available in the literature.

Studies of thin strained InAs, AlAs, and AlSb layers by spectroscopic ellipsometry

“…The calculated and experimentally determined shifts for the E 1 CPs are in good qualitative agreement, as in Refs. [25][26][27][28]. For E 1 , the hydrostatic and uniaxial components of the strain effect have opposite signs and compensate each other predicting a small energy change as is observed experimentally.…”

Nondestructive characterization of semiconductor multilayers

“…If the mixing is on an atomic scale, however, as in a true alloy, the EMA cannot be used, This is because alloying produces a change in the band structure and shifts in the energy gaps, or critical point (CP) transition energies, This is illustrated in Figure 2, which shows reference spectra for strained Sil_xCe x determined by SE. 6 The peaks in the spectra are due to strong absorption occurring at E 1 , E1 + t:.., (Eo') transitions near 3,25 eV and E2 transitions at 4,25 eV. The EI' EI + t:..1 peaks move monotonically to lower energy with increasing x.…”

“…where ~ = 41tt( n~ -sin 2 <1>Yl2/A and fi, is the refractive index of the layer of thickness t. The quantities r;,p and rs:~ are the reflectance coefficients at the aIr/layer and layer / substrate boundaries, respectively, For multilayers, Equation 6 may be extended using a matrix approach; however, the equations cannot be inverted to obtain fi, and t. A regression analysis approach is used, in which a model is hypothesized and i' and i's' and hence 'I' and t:.., are calculated using …”

“…Oxide thickness values of 4-7 A were estimated as described previously. 6 The effect of strain is to produce an increased splitting of the EI and EI + ~ peaks,20,21 producing the shoulder in EI at 3.25 eV for x = 0.23 in Figure 2, and a consequent reduction in n at low energies. 6 A similar effect has been observed 22 in InxGal_xAs on GaAs, as shown in Figure 6.…”

Ellipsometry and Its Applications in Stoichiometry

“…al. applied SE to study thick, relaxed and thin, strained epilayers of Si 1-x Ge x on Si in the range 0 <x <0.25 which is the range of importance for the SiGe HBT [92][93][94]. In Fig.…”