Study on the lattice structure of InAsPSb thin-film grown on GaAs
Date Issued
2012
Date
2012
Author(s)
Chen, Kuan-Ta
Abstract
In this thesis, a series of InAsPSb with different composition was grown on GaAs substrate by a GSMBE system. We study the lattice structure characteristics of InAsPSb alloy on small lattice constant of GaAs substrate.
We used EPMA to collect the composition of InAsPSb sample and used High Resolution X-ray diffraction to collect the (0 0 4) and (-1 -1 5) reciprocal space mapping (RSM) for InAsPSb. And we got the Horizontal and vertical lattice constant of InAsPSb sample by the reciprocal space mapping analysis. From RSM results, we found the trend of strain in these InAsPSb samples; the higher the As composition and the larger the strain. Further more, we used valence force field (VFF) model to calculate the distortion energy of several 512-atom InAsPSb supercells of 4×4×4 lattice size with different As composition. VFF calculation reveals that the percentage change in distortion energy increases with the increasing As composition, which could explain the trend of strain in InAsPSb.
Besides, we also studied the P, As, In-kedge x-ray absorption spectra of InAsPSb alloy by synchrotron radiation. We used the first shell atom model to fit the fourier transformed extended X-ray absorption fine structure (EXAFS) signals. In P-kedge analysis, We used the energy calibration for the energy error of double crystal monochromator. In As-kedge, due to the attenuation of signal strength by measurement method, we used self absorption correction to compensate signal. Due to the above two methods, we could get more accurate EXAFS results. Futher more, The VFF calculated interatomic distance in InAsPSb is almost independent on the As mole fraction and in good agreement with the EXAFS measurement. And the EXAFS results support the results of InAsPSb alloy internal structure by the RSM and VFF analysis.
Subjects
InAsPSb
RSM
synchrotron radiation
Type
thesis
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