NOVEL TECHNIQUES FOR CHARACTERIZING DETECTOR MATERIALS USING PULSED INFRARED SYNCHROTRON-RADIATION

The VUV ring at the National Synchrotron Light Source (NSLS, Brookhave n National Laboratory) is a source of nanosecond-duration, high-bright ness, broadband IR pulses. We are developing several measurement techn iques for characterizing Hg1-xCdxTe and other IR detector materials us ing this source. For example, the broadband IR pulses can be used to s tudy transient photoconductive decay at various photon energies near t he bandgap. A particularly novel technique we have developed is far-in frared photoinduced nanosecond spectroscopy (FIR-PINS). In this all-op tical (contactless) measurement, a short laser pulse generates photoca rriers which are subsequently sensed by a far-infrared pulse from the synchrotron. Spectroscopic analysis of the far-infrared yields the fre e carrier plasma frequency, providing information on the photocarrier density. By varying the delay time of the far-infrared pulse (relative to the laser pulse), the photocarrier relaxation is determined with n anosecond resolution. In addition to being contactless, the technique offers other potential advantages over electrical measurements. Result s for MBE-grown Hg1-xCdxTe are presented.