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Real-time Characterization of the Optical Properties of an ultra-thin Surface Reaction Layer during Growth

Published online by Cambridge University Press:  10 February 2011

N. Dietz
Affiliation:
Departments of Physicsa Materials Science and Engineering
N. Sukidib
Affiliation:
Materials Science and Engineering
C. Harrisb
Affiliation:
Materials Science and Engineering
K. J. Bachmann
Affiliation:
Departments of Physicsa Chemical Engineeringc, North Carolina State University, Raleigh, North Carolina 27696-7919
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Abstract

The average optical properties of an ultra-thin surface reaction layer (SRL) during growth by pulsed chemical beam epitaxy (PCBE) can be quantitatively accessed by p-polarized reflectance spectroscopy (PRS), as demonstrated on the example of heteroepitaxial GaP growth. Under PCBE growth conditions, the surface of the substrate is exposed to pulsed ballistic beams of tertiarybutyl phosphine [TBP, (C4H9)PH2] and triethylgallium [TEG, Ga(C2H5)3]. The pulsed precursor supply causes a period in composition and thickness modulated SRL, monitored as a fine structure that is superimposed on interference oscillations, resulting from back reflection at the substratelayer interface with increasing layer thickness. The amplitude of this fine structure undergoes a period amplitude modulation and exhibits turning points at which the response to the first precursor pulse changes sign. The turning points can be characterized by the expression R4max)=R4min), which describes the maximal and minimal values of the temporally modulated phase factor in the SRL, using a four layer stack description. The positions of these turning points are not affected by the thickness of the SRL, which allows the computation of the average complex dielectric function of the SRL independent of its thickness. In the next step, the average thickness of the SRL can be extracted from the amplitude of the observed fine structure.

Type
Research Article
Copyright
Copyright © Materials Research Society 1997

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