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

Differential carrier lifetime measurements were performed on index-guided o xide-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 mode l. The carrier lifetimes ranged from 21 ns at 9 mu A,to about 1 ns at a bia s close to threshold. For a 6X6 mu m(2) oxide aperture device the threshold carrier density was n(th)similar to 2X10(18) cm(-3). The effect of carrier diffusion was also considered. An ambipolar diffusion coefficient of D sim ilar to 11 cm(2) s(-1) was obtained. (C) 1999 American Institute of Physics . [S0003-6951(99)00507-0].