Carrier capture times in quantum-well, -wire, and -box distributed-feedback lasers characterized by dynamic lasing emission measurements

Abstract

We report experimental and theoretical studies of carrier capture times in low-dimensional semiconductor distributed feedback lasers with three different typical active region structures: quantum well (QW), wire, and box. The total effective carrier capture times of the lasers are directly determined by means of dynamic lasing emission measurements. By systematical comparison of QW, wire and box lasers, we evidence a strong dependence of the total effective carrier capture time on the packing density of the active region, which indicates the significant contribution of the local quantum capture time to the total effective carrier capture time, as revealed firstly by Kan et al. (1993). The intrinsic local carrier quantum capture time can be deduced from this kind of study. The determined local quantum carrier capture time for the InGaAs-InGaAsP QW laser is about 3 ps at 2 K, which is well consistent with a detailed quantum mechanics calculation. Furthermore, by comparison of box lasers with an approximate equal box size (70 nm) but different box densities, we find that the determined local quantum capture time of the box lasers is only about 2.4 ps at low temperature. We believe that this is a direct experimental indication of the existence of an efficient channel for carrier capture and relaxation in the investigated quantum-box system. The systematic comparison of QW, wire and dot lasers reveals the dominant limitation of the geometry effect on the high speed modulation of quantum wire and dot lasers, except when the quantum wires and dots are packed with a quite high density.