Spontaneous emission lifetime of carriers in a semiconductor microcavity measured by photoluminescence without distortion by reabsorption

A theory for carrier decay rates and a technique for measuring them are rep orted. Modification of the spontaneous emission rate of carriers by a semic onductor microcavity is investigated with 100-nm-thick bulk GaAs. Reabsorpt ion makes the cavity-mode photoluminescence (PL) decay much faster than the square of the carrier density. Here reabsorption distortion is avoided by collecting PL that escapes the microcavity directly without multiple reflec tions: a ZnSe prism glued to the top mirror allows PL to escape at angles b eyond the cutoff angle for total internal reflection without the prism. At these steep angles, the stop band of the top mirror has shifted to higher e nergy, so that it does not impede PL emission. Removal of most of the botto m mirror decreases the true carrier decay rate by only approximate to 25%, showing that the large enhancements deduced from cavity-mode PL are incorre ct. Fully quantum mechanical computation including guided modes corroborate s this conclusion. The prism technique could be used to study carrier dynam ics and competition between guided and cavity modes in microcavities below and near threshold. (C) 1999 Optical Society of America.