Measurement of Free-Carrier Lifetimes in GaP by Photoinduced Modulation of Infrared Absorption

A new technique is presented for measuring the lifetimes of both minority and majority photoexcited free carriers in GaP. The technique is useful for both n- and p- type material in any doping range and involves measurement of the modulation of the free-carrier infrared absorption induced by photoexcited free carriers. In GaP(Zn, O) we find that the minority-carrier (electron) lifetime ranges from 1 to 20 nsec, and the majority-carrier (hole) lifetime ranges from 0.1 to 2 μ sec. A saturation effect is observed which is consistent with the view that the dominant recombination path in GaP(Zn, O) is through a deep acceptor via an Auger mechanism.