SELF-ABSORPTION AND FOCUSING EFFECTS IN CARRIER RELAXATION DYNAMICS UNDER DEPLETION CONDITIONS

The effect of a one-dimensional field (1) on the self-absorption chara cteristics and (2) when we have a finite numerical aperture for the ob jective lens that focuses the laser beam on the solid are considered h ere. Self-absorption, in particular its manifestation as an inner filt er for the emitted signal, has been observed in luminescence experimen ts. Models for this effect exist and have been analyzed, but only in t he absence of space charge. Using our previous results on minority car rier relaxation in the presence of a field, we obtain expressions inco rporating inner filter effects. Focusing of a light beam on the sample , by an objective lens, results in a three-dimensional source and cons equently a three-dimensional continuity equation to be solved for the minority carrier concentration. Assuming a one-dimensional electric fi eld and employing Fourier-Bessel transforms, we recast the problem of carrier relaxation and solve the same via an identity that relates it to solutions obtained in the absence of focusing effects. The inner fi lter effect as well as focusing introduces new time scales in the prob lem of carrier relaxation. The interplay between the electric field an d the parameters which characterize these effects and the consequent m odulation of the intensity and time scales of carrier decay signals ar e analyzed and discussed.