Differential carrier lifetime in oxide-confined vertical cavity lasers obtained from electrical impedance measurements

Abstract

Differential carrier lifetime measurements were performed on index-guided oxide-confined vertical cavity surface emitting lasers operating at 980 nm. Lifetimes were extracted from laser impedance measurements at subthreshold currents, with device size as a parameter, using a simple small-signal model. The carrier lifetimes ranged from 21 ns at 9 µA, to about 1 ns at a bias close to threshold. For a 6 × 6 µm2 oxide aperture device the threshold carrier density was nth ~ 2 × 1018cm-3. The effect of carrier diffusion was also considered. An ambipolar diffusion coefficient of D ~ 11 cm2s-1 was obtained.