621.315The dependence of active and reactive components of the admittance of MIS structures based on heteroepitaxial Hg 0.78 Cd 0.22 Te produced by molecular-beam epitaxy as a function of bias voltage is experimentally studied in the frequency range 1 kHz -1 МHz. The resistance of the epitaxial-film volume is shown to significantly affect the measured admittance in the case where the electron concentration in HgCdTe is up to 5⋅10 14 cm -3 , and this is manifested in a number of features of the capacity-voltage characteristics. The resistance of the epitaxial-film volume is found for the samples with different initial conductivity and for the samples with graded-band subsurface layers. The techniques are proposed that make it possible to avoid the influence of volume resistance on the admittance of MIS structures on the basis of heteroepitaxial HgCdTe.
The initial stages of the growth of germanium on the dimer reconstructed Si(100) surface is modelled using molecular dynamics (MD). Pyramidal island structures are observed to form despite MD being carried out at a deposition rate faster than experiment. By an examination of transitions that can occur from intermediate structures that form in the MD simulations, growth mechanisms can be identified. The initial wetting occurs as a result of Ge atoms diffusing into the trenches between the dimer rows. This results in Ge-Ge or Ge-Si dimer chains growing in rows perpendicular to the original Si-Si dimer rows on the surface. It is shown how strained Ge pyramids with square bases can form by diffusing atoms joining together adjacent dimer rows. From these initial square-based structures, complex concerted motions are observed in which atoms in lower layers 'climb up' to higher layers. Similar structures grown in the pure Si case exhibit much higher energy barriers for the 'climbing up' process indicating that the effect of strain is to reduce the energy barriers for pyramid formation. In addition to the investigation of atomistic growth processes, surface energy effects are also examined, which show that a germanium-covered Si(100) surface containing shallow-angled pyramids is energetically more favourable than that grown as a flat monolayer.
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