Investigation of surface recombination and carrier lifetime in 4H/6H-SiC

A spatially and time-resolved free carrier absorption method is applied to quantify surface recombination losses as compared to the bulk in 4H- and 6H -SiC structures. The observed carrier lifetime variation is discussed in te rms of crystalline quality, top-surface properties and junction effects at the epilayer-substrate interface. Surface recombination parameters in epila yers with differently processed surfaces are extracted from fitting experim ental data with numerical simulations. The as-grown bare epilayer is charac terized by 10(4) cm s(-1) surface recombination velocity. Mechanical polish ing increases this parameter to 5 x 10(5) cm s(-1). No noticeable passivati on of GH-SIC surface by an oxide film is observed, whereas an increase of t he surface recombination velocity up to 105 cm s(-1) has been detected afte r dry oxidation of 4H-SiC. (C) 1999 Elsevier Science S.A. All rights reserv ed.