In the previous beamtime, RB1520457, we have found that the relaxation rate can be used as a measure of the photocarrier density in intrinsic silicon. This method has been applied to measure the lifetime of photocarriers in two different temperatures. In this proposal we continue to measure the lifetime and its temperature dependence in doped silicon samples, which are important in many semiconductor applications. We also expect to observe an interaction between Mu and photoexcited minority carriers in doped silicon.