NONCONTACT LIFETIME SCREENING TECHNIQUE FOR HGCDTE USING TRANSIENT MILLIMETER-WAVE REFLECTANCE

A non-contact lifetime screening technique for measuring excess carrie r lifetime in HgCdTe (MCT) using transient millimetre-wave reflectance (TMR) is presented. The TMR system described is capable of measuring lifetimes ranging from less than or similar to 10 ns found in high-dop ed (greater than or similar to 1 x 10(16) cm-3) p-type material to > 1 mus found in low-doped (less than or similar to 1 x 10(15) cm-3) n-ty pe material. In TMR the reflected 90 GHz millimetre-wave (mm-wave) sig nal is proportional to a transient change in photoconductivity induced by a short (1.06 mum) YAG laser pulse. The details of the TMR test sy stem including the mm-wave circuit design are described. The system us es a computer controller for 80-300 K temperature control, x-y wafer t ranslation and data acquisition and analysis. The TMR technique is sho wn to be equivalent to standard photoconductive decay. Applications of the technique, including MCT epilayer characterization by both fronts ide and backside illumination and in-process wafer characterization, a re discussed. Spatial mapping of lifetime over an MCT wafer is demonst rated.