Spectroscopic ellipsometry characterization of strained and relaxed Si1−xGex epitaxial layers

Abstract

Spectroscopic ellipsometry has been used to study thick, relaxed and thin, strained epilayers of Sil-,Ge, on Si in the range 0.1 <x ~0.25. Dielectric functions of relaxed Sios,GeO,ls and Sic,sGec, have been obtained and long-wavelength absorption coefficient values, required for interference fringe fitting, shown to be higher than measured previously. The dielectric function of strained Si0.,sGec2z has been measured for the first time and the effects of strain on the critical points shown to be consistent with deformation potential theory. An interpolation procedure has been developed for the fitting of layer composition and thickness, and excellent agreement with conventional techniques obtained for a series of uncapped single epilayers. The surface roughness of Sit-,Ge, epilayers has been studied as a function of time and deposition temperature and shown to play an important role in the modeling. The application of the technique to the characterization of buried strained layers is discussed.

Composition dependence of the interband critical points in Si1−xGex alloys: A fractional–dimensional space approach

“…Using the standard line-shape analysis, Humlicek et al 7 employed a two-dimensional model for CP E 1 , while Pickering et al 8 employed an excitonic model. Despite using a totally different dimensional model ͑2D versus excitonic͒, both Refs.…”

“…1 Although there have been many reports on the interband transitions in Si or Ge, [2][3][4][5][6] there are comparatively few on SiGe alloys. Several researchers have analyzed the compositional dependence of critical point ͑CP͒ energies of relaxed bulk Si 1Ϫx Ge x alloys using the standard line-shape fitting analysis, 7,8 but the compositional dependence of other CP parameters has not been established. Possible reasons for this lack are as follows: first, the values of these parameters are affected by the dimensional model adopted for the standard line-shape analysis; [2][3][4]9 second, their compositional dependence is complex due to well-known alloying effects.…”

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

“…20 The critical thickness decreases with increasing mis~atch. For Sil_xGe x grown on Si, -500 A thick layers are fully strained at x = 0.2, while for InxGal_xAs grown on GaAs <200 A layers are required for x = 0.25, due to the larger lattice mismatch.…”