Determination of interface recombination velocities and carrier lifetimes in SOI materials by a contactless optical modulation technique

Abstract

A novel contactless dual-beam optical modulation (DBOM) technique has been employed for determining the interface recombination velocities and substrate carrier lifetimes in a SIMOX (Separation by IMplantation of OXygen) wafer. The DBOM method utilizes the optical modulation of the transmitted light intensity of an infrared (i.r.) probe beam ( hv < E g) modulated by a CW visible laser pump beam ( hv > E g) of different wavelengths (e.g., λ = 442 and 632.8 nm) via free-carrier absorption in the SIMOX wafer. The interface and bulk recombination velocities were determined by using pump beams of different wavelengths and incident angles. A theoretical model for the DBOM technique has been developed for extracting the interface recombination velocities and substrate lifetimes in the SIMOX wafers. The front-interface [Si film/buried oxide layer (BOX) interface] and back-interface (BOX/Si substrate interface) recombination velocities as well as the substrate carrier lifetimes were determined using this new technique. Mappings of the front- and back-interface recombination velocities and the substrate carrier lifetimes for several SIMOX wafers with different Si film thicknesses and oxygen implantation processes have been carried out.