Minority Carrier Lifetime Mapping System for High Energy Physics Semiconductor Materials

Novel, high performance semiconductor detectors are needed for future dark matter and dark energy exploration projects initiated by the Department of Energy, Office of High Energy Physics. In-situ measurement of minority carrier recombination lifetime and lifetime distribution along entire wafer/brick/ingot surfaces are required to evaluate the semiconductor materials used for detector fabrication and to optimize the detector fabrication processing procedures. In response to the DOE’s requirements, EPIR proposes to fabricate and deliver a minority carrier lifetime mapping system that will measure the carrier recombination lifetime and two-dimensional lifetime distributions. We plan to use a pulse semiconductor laser with rise/decay time less than 0.5ns as excitation source and a long- wavelength-infrared (LWIR) laser as a probe light. The laser pulse will generate the excess carriers that will lead to increased free carrier absorption, proportional to the excess carrier concentration. Free carrier absorption decay will be detected using a fast (2 GHz bandwidth) LWIR HgCdTe detector. EPIR will fabricate the LWIR detector using in-house grown HgCdTe material and detector fabrication technology. High speed analog to digital convertor boards will be used to digitalize the time-dependent signal. A two-dimensional scanner will be built for mapping and scanning measurements up to 15 inch × 19 inch, sufficient for any large area semiconductor wafers. With further maturation of the measurement system and technology, our proposed system can also be integrated in other semiconductor material evaluation and device fabrication lines, including the ones used for radiation/infrared detectors and light emission devices