Study of epitaxial selective area growth In1−xGaxAs films by synchrotron μ-XRF mapping

Abstract

We present an analytical method allowing to quantitatively extract, from a space resolved Synchrotron Radiation X-Ray Fluorescence (SR-XRF) map, the variation of the thickness and chemical composition of a In1−xGaxAs ternary semiconductor film, in which a gradient in the growth plane of both composition and thickness is obtained using the Selective Area Growth (SAG) method. This advanced growth technique allows the realization of monolithic integrated laser/modulator devices for long distance fiber optics communication at high frequency, which have recently come to the market as high performance products. In a SAG growth, the optimization of the growth parameters is usually done by an empirical approach since a spatially resolved compositional characterization is not possible with conventional laboratory techniques. Exploiting the μ-X-ray beam available at the ID22 beamline of the European Synchrotron Radiation Facility (ESRF), we performed a 2D micrometric resolved (1.7 × 5.3 μm2) XRF study of a In1−xGaxAs ternary semiconductor film. The purposed method is a theoretical influence coefficient algorithm based on the use of only few reference materials coupled with the fundamental parameter (FP) approach and it is optimized for intermediate thickness samples. Reported values agree quantitatively with independent High Resolution X-Ray Diffraction (HRXRD) analysis within 1%.