The effect of illumination power density on carbon defect configuration in silicon doped GaN

A study of efficacy of point defect reduction via Fermi level control during growth of GaN:Si as a function of above bandgap illumination power density and hence excess minority carrier density is presented. Electrical characterization revealed an almost two-fold increase in carrier concentration and a three-fold increase in mobility by increasing the illumination power density from 0 to 1 W cm−2, corroborating a decrease in compensation and ionic impurity scattering. The effect was further supported by the photoluminescence studies, which showed a monotonic decrease in yellow luminescence (attributed to CN) as a function of illumination power density. Secondary ion mass spectroscopy studies showed no effect of illumination on the total incorporation of Si or C. Thus, it is concluded that Fermi level management changed the configuration of the C impurity as the CN −1 configuration became energetically less favorable due to excess minority carriers.