Composition and thickness control of thin LPE HgCdTe layers using x-ray diffraction
Double-axis x-ray rocking curve measurements have been used to nondestructively characterize the composition profile of HgCdTe heterojunction photodiode structures grown by liquid phase epitaxy (LPE). In particular, the thickness and composition profile of the thin graded-composition cap layer are determined through an empirical correlation between rocking curve parameters and composition profiles measured by SIMS. Spatial maps of cap layer thickness and composition are generated from automated measurements of x-ray rocking curves across a wafer. X-ray mapping has been instrumental in improving the spatial uniformity of cap layers and in maintaining control of the growth process in Hg-rich LPE dipping reactors.