CARRIER CAPTURE TIMES IN QUANTUM-WELL, QUANTUM-WIRE, AND QUANTUM-BOX DISTRIBUTED-FEEDBACK LASERS CHARACTERIZED BY DYNAMIC LASING EMISSION MEASUREMENTS

We report experimental and theoretical studies of carrier capture time s in low-dimensional semiconductor distributed feedback lasers with th ree different typical active region structures: quantum well (QW), wir e, and box, The total effective carrier capture times of the lasers ar e 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. The intrisinc local carrier quantum capture time can be deduced from this kind of st udy, 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 b ox densities, we find that the determined local quantum capture time o f the box lasers is only about 2.4 ps at low temperature, We believe t hat this is a direct experimental indication of existence of an effici ent channel for carrier capture and relaxation in the investigated qua ntum-box system, The systematic comparison of QW, wire and dot lasers reveals the dominant limitation of geometry effect on the high speed m odulation of quantum wire and dot lasers except when the quantum wires and dots are packed with a quite high density.