In the last few decades, high performance electronic and optoelectronic devices based on semiconductor heterostructures have been required to obtain increasingly strict and well defined performances, needing a precise control, at the atomic level, of the structural composition of the buried interfaces. This goal has been achieved by an improvement of the epitaxial growth techniques and by the parallel use of increasingly sophisticated characterization techniques. Among them, a leading role is certainly played by those exploiting synchrotron radiation sources. In fact synchrotron radiation has distinct advantages as a photon source, notably high brilliance and continuous energy spectrum; by using the latter characteristic, atomic selectivity can be obtained. This is of fundamental help to investigate the structural environment of atoms present only in a few angstrom thick interface layers of heterostructures. The third generation synchrotron radiation sources have allowed to reach the limit of measuring a monolayer of material, corresponding to about 1014 atoms/cm2. This chapter presents important results obtained by several groups in the characterization of III-V thin films and superlattices using extended x-ray absorption fine structure (EXAFS). When needed for comparison, comments on a few relevant studies of II-VI and IV-IV heterojunctions will also be included. Particular emphasis will be given to: (i) the role of alloying determining the first-shell bond distances in pseudo-binary alloys of the type AxB1-xC; (ii) the joint role of alloying and epitaxy in determining the first-shell bond distances in strained thin epitaxial layers; (iii) the problem of multiple scattering in the higher shell studies; and (iv) the interface characterization of superlattices. Finally, a few examples are reported on related techniques such as surface EXAFS (SEXAFS), diffraction anomalous fine structure (DAFS) and x-ray standing waves (XSW) in the characterization of III-V thin films and heterostructures.
The use of EXAFS spectroscopy related techniques in the characterization of III-V thin films heterostructures
LAMBERTI, Carlo
2003-01-01
Abstract
In the last few decades, high performance electronic and optoelectronic devices based on semiconductor heterostructures have been required to obtain increasingly strict and well defined performances, needing a precise control, at the atomic level, of the structural composition of the buried interfaces. This goal has been achieved by an improvement of the epitaxial growth techniques and by the parallel use of increasingly sophisticated characterization techniques. Among them, a leading role is certainly played by those exploiting synchrotron radiation sources. In fact synchrotron radiation has distinct advantages as a photon source, notably high brilliance and continuous energy spectrum; by using the latter characteristic, atomic selectivity can be obtained. This is of fundamental help to investigate the structural environment of atoms present only in a few angstrom thick interface layers of heterostructures. The third generation synchrotron radiation sources have allowed to reach the limit of measuring a monolayer of material, corresponding to about 1014 atoms/cm2. This chapter presents important results obtained by several groups in the characterization of III-V thin films and superlattices using extended x-ray absorption fine structure (EXAFS). When needed for comparison, comments on a few relevant studies of II-VI and IV-IV heterojunctions will also be included. Particular emphasis will be given to: (i) the role of alloying determining the first-shell bond distances in pseudo-binary alloys of the type AxB1-xC; (ii) the joint role of alloying and epitaxy in determining the first-shell bond distances in strained thin epitaxial layers; (iii) the problem of multiple scattering in the higher shell studies; and (iv) the interface characterization of superlattices. Finally, a few examples are reported on related techniques such as surface EXAFS (SEXAFS), diffraction anomalous fine structure (DAFS) and x-ray standing waves (XSW) in the characterization of III-V thin films and heterostructures.
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