Understanding and controlling the CuPt ordering in epitaxially grown InGaP2 is essential to the continued development of high performance, reliable multi-junction solar cells. Dr. Ryan France of the U.S. Department of Energy’s National Renewable Energy Laboratory in Golden, Colorado recently reported the in situ measurement of CuPt ordering in MOVPE grown InGaP2 using strain anisotropy. In this research, Dr. France was able to use the kSA MOS system to measure the wafer curvature and thus the strain in his epitaxial films during film growth. Since the kSA MOS system offers a two-dimensional array of laser spots, he was able to measure the wafer curvature in two orthogonal directions simultaneously. By properly aligning his sample to this array, the kSA MOS system measured the curvature in the [-110] and [110] directions. Then, by comparing the difference in curvature in these two directions and calculating the resulting strain anisotropy, he was able to relate these parameters with the ordering parameter and the material bandgap measured ex situ by X-ray diffraction (XRD) and photoluminescence (PL), respectively. Dr. France believes that “this technique can be used to rapidly determine the growth condition dependence of ordering in III-V alloys and to monitor the order-disorder transitions.”
For more information please see Dr. France’s article in the Journal of Applied Physics.
“In situ measurement of CuPt alloy ordering using strain anisotropy”, Ryan M. France, William E. McMahon, Joongoo Kang, Myles A. Steiner, and John F. Geisz, Journal of Applied Physics, 115, 053502, 2014.
