Mapping of Elements and Microstructures in a Crystal

Semiconductor crystals synthesized using three elements together from group III and Group IV of the periodic table are attracting attention of the researchers due to their adjustable energy band gap depending on the composition ratio. Elemental mapping is one of the powerful techniques to find exact composition ratio and the distribution of the elements in the crystal structure. By adopting the vertical directional solidification (VDS) process, a III-V ternary bulk crystal (ingot) using Indium, Antimony, and Bismuth as the source materials (InSb1-xBix) was formed. The grown ingot was then cut into wafers. Further, the surface characterization of the formed crystal was done using the well-polished wafers. With a resistivity of 1.00 X 10-3 ohm-cm, the resistivity measurement revealed that the wafers were n-type semiconductors. These wafers were lapped and polished to get mirror finish surface. After cleaning the wafers were etched by using CP4 (HNO3: HF:CH3COOH: 5:3:3) and the modified CP4 (HNO3: HF: CH3COOH:H20::5:3:3:10) etchants. The microstructures and defects on the surface of the wafers (substrates) were studied using metallurgical microscope. SEM and EDAX techniques were used for the further analysis of the microstructures observed during the microscopic analysis. Most of the surface is uniformly configured, but there are certain flaws like black spots, dents, and grain boundaries. The results of the EDAX analysis show that Bi-rich domains have formed. By conducting an elemental examination of the surface, the compositional elements' distribution was investigated. High resolution SEM analysis of a dent reveals the formation of nano-crystals of size ~ 150nm.