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Phase fluorometry for semiconductor lifetime measurement

Understanding and quantifying nonradiative recombination is a critical factor for the successful laser cooling of semiconductors. The usual approach to measuring the nonradiative lifetime employs pulsed photoexcitation and monitors the luminescence decay via time-resolved photon counting. We present an alternative approach that employs phase fluorometry with a lock-in amplifier. A sinusoidally modulated diode laser is used for excitation. Lifetime data are extracted from the frequency dependent phase shift and amplitude response of the photolumi-nescence signal, detected by a photomultiplier tube. Samples studied include high quality AlGaAs/GaAs/AlGaAs and GaInP/GaAs/GaInP double heterostructures, grown by MBE and MOCVD. Data over a temperature range from 10 to 300 K is compared with results obtained in time-domain measurements.