HIGH-SPATIAL-RESOLUTION RESISTIVITY MAPPING APPLIED TO MERCURY CADMIUM TELLURIDE

The fine-scale resistivity variations of slices of bulk, n-type Hg1-xCdxTe (HgCdTe) grown by the solid-state recrystallization (SSR) process and thin-film epitaxial layers of HgCdTe grown by liquid phase epitaxy (LPE) on SSR substrates were mapped at room temperature (297 K). An automatic probe station was used to make four-probe resistance measurements, spaced 80-mu-m apart, on lithographically defined metal-to-HgCdTe contacts. Most slices of SSR HgCdTe were found to have resistivities that increased from the center to the outside edge, and some SSR material also showed small inclusions with resistivity either higher or lower than the surrounding material. LPE material was found to have a more random variation in resistivity than SSR HgCdTe material. Also, the metal-semiconductor contact resistivity of In/Pb/In/Ni contacts to n-type HgCdTe was measured to be in the range of 0.3 to 20 X 10(-5) OMEGA-cm2 for HgCdTe resistivities varying from 0.01 to 0.1-OMEGA-cm.