Spectroscopic ellipsometry of Si1−xGex epilayers of arbitrary composition 0≤x≤0.255

Abstract

Critical point (CP) transition energies have been calculated for strained Si1−xGex (0≤x≤0.255) between 2.5 and 3.5 eV from Lorentzian fits to the second differential of reference dielectric function spectra. E1 and E′0 transition energies are similar to those of the relaxed alloy. Comparison with deformation potential theory shows E1+Δ1 to be coincident with E′0 due to a strain-induced up shift in the former’s transition energy. The reference spectra and CP transition energies are used in an interpolation procedure to analyze spectroscopic ellipsometry spectra of both uncapped and buried layers of strained Si1−xGex. Compositions and thicknesses are obtained in good agreement with alternative techniques.

Pulsed laser crystallization of silicon–germanium films

“…where C is crystalline volume ratio, n c and n a are the complex refractive indexes of single-crystalline and amorphous SiGe [16][17][18][19]. The best fitting of the calculated reflectivity spectra to experimental ones gave the crystalline volume ratio.…”

Spectroscopic ellipsometry for monitoring and control of surfaces, thin layers and interfaces

“…For example, in Si 1 x Ge x and other strained layer alloys the effect of strain is to increase splitting of the E 1 and E 1 C  1 peaks. 15,16 This is illustrated in Fig. 6, which compares ε 2 and second-derivative spectra from a strained 100Å and a relaxed 1 µm In 0.24 Ga 0.76 As layer grown on GaAs.…”

“…An interpolation procedure is used to represent the alloy, based on polynomials for each critical point variation with composition. 13,15 The critical point energies also are affected by strain and temperature through changes to the band structure. For example, in Si 1 x Ge x and other strained layer alloys the effect of strain is to increase splitting of the E 1 and E 1 C  1 peaks.…”

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.…”