Spatially and time-resolved infrared absorption for optical and electricalcharacterization of indirect band gap semiconductors

The current status of the spatially and time-resolved free-carrier absorpti on (FCA) method is provided. The FCA technique allows monitoring carrier dy namics in a time scale from nanoseconds to miliseconds by employing either collinear or orthogonal geometry between pump and probe beams. A high spati al resolution is achieved allowing in-depth carrier profiles to be extracte d. The method is particularly suited for investigation of injection-depende nt optical and recombination phenomena: band gap optical absorption, Shockl ey-Read-Hall (SRH) lifetime, Auger recombination coefficient, and the injec tion-dependent surface (interface) recombination velocity. We summarize imp ortant aspects of the technique demonstrating numerous measurements that ha ve been implemented in studies of bulk Si, epilaxial 4H-SiC and porous sili con. (C) 2000 Elsevier Science S.A. All rights reserved.