Study of the single-particle energy spectrum of disordered systems: III. The two-band case

Unger, H.-J.

doi:10.1007/bf01312757

Cited by 2 publications

(3 citation statements)

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“…Other global parameters reflecting in peculiarities of the density of states do not exist, in particular there are no van-Hove singularities in disordered systems which could influence the asymptotic behaviour of the recursion coefficients. Consequently, the tridiagonalization of the effective medium Hamiltonian must rapidly converge to a characteristic chain the parameters of which yield the mobility edges [23, 241. In the one-band case this is the constant chain [23, 241 and in two-or more-band cases the periodic chain [25]. The chain tails obtained in such a way serve to terminate the finite chains numerically generated in the recursion method.…”

Section: (44)mentioning

confidence: 99%

“…Note that the pseudogap behaviour at the mobility edges is closely related with the divergence of the localization length at the mobility edges [25]. If a disordered system possesses mobility edges, then the proposed kind of termination of the chains of recursion coefficients can be assumed to be valid and Fig.…”

Section: Two-band System Of Amorphous Silicon or Germaniummentioning

confidence: 99%

“…This method has the advantage that the thermodynamic limit is carried out. The typical form of the TDS for a two-band system which can be obtained from such a calculation [25] is represented in Fig. 2.…”

Section: Two-band System Of Amorphous Silicon or Germaniummentioning

confidence: 99%

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Covalent Bonds in Amorphous Semiconductors and Their Influence on the Structure of the Energy Spectrum

Unger¹

1990

Physica Status Solidi (b)

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The structure of the energy spectrum of amorphous semiconductors as determined by the formation of covalent bonds is analyzed. In contrast with other theoretical models all considerations are based on a realistic model of the atomic structure of a-Si and a-Ge. The mathematical method used throughout the paper is, within certain subspaces (cells) of the total Hilbert space, the partial diagonalization of the Hamiltonian represented in an "extended Hilbert space". Existing model Hamiltonians, e.g. the Weaire-Thorpe model, are generalized in such a way that real disordered solids can be described. The molecular model used in this paper yields the basic feature of the structure of the energy spectrum. For positionally disordered systems an Anderson-like Hamiltonian is obtained. The formation of extended and localized states in disordered solids is explained by taking into account the residual interactions. Conditions for the localization of electronic states and the existence of mobility edges depending on the local and global atomic structure of amorphous semiconductors are given. A generalization of the cell model in the spirit of the scaling theory of localization leads to a method for the determination of the position of the mobility edges. Structural correlation in amorphous semiconductors manifesting itself in short-range order and in the existence of voids, which is not taken into account e.g. in the Anderson model, is found to be the origin of the basic structural properties of the energy spectrum of disordered semiconductors. Conclusions from the theory proposed are in accordance with experimental findings and explain them.

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Section: (44)mentioning

confidence: 99%

Section: Two-band System Of Amorphous Silicon or Germaniummentioning

confidence: 99%