Proceedings PaperMinority Carrier Lifetime Mapping In Gallium Arsenide By Time-Resolved Photoluminescence Scanning Microscopy
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The minority carrier lifetime in gallium arsenide (GaAs) can be determined from time-resolved photolumi-nescence near the optical band edge, around 872 nm (1.42 eV) at room temperature. Spatial resolution of the order of a few micron is required for investigating microscopic fluctuations of he minority carrier lifetime in GaAs materials and in small, highly integrated devices. A photoluminescence lifetime spectrometer (PLS) based on the time-correlated single photon counting (TCSPC) technique was developed for this purpose. The instrument uses only solid state components, i.e. pulsed diode laser excitation and single photon avalanche diode (SPAD) detection, and is capable of measuring photoluminescence decay time constants of the order of 10 ps with 3 μm spatial resolution. Operation at a repetition rate above 50 MHz reduces the data collection time for a complete decay curve to a few seconds and thus permits one and two-dimensional scans to be done. The design of the PLS is discussed and first results from LEC grown GaAs substrates are presented.