Wetting layer entropy effect on the modulation response of self-organized quantum dot lasers

Abstract

Self-organized quantum dot (QD) lasers are rapidly advancing with impressive demonstrations of extended wavelength operation beyond 1.3 /spl mu/m for GaAs-based devices, and very low threshold current density and current. However, the modulation response of these unique devices has not yet been heavily studied. Because of the radically altered density of electronic levels due to the 0-dimensional (0-D) confinement, we may expect modulation behavior significantly different than for the heavily studied planar quantum well lasers. Early predictions were that the QD modulation response may be improved over planar quantum wells due to a larger differential gain. However, the first experimental reports comparing the small-signal modulation of self-organized QD lasers to that for planar quantum well lasers show that the QD lasers have a much stronger temperature sensitivity, and a much lower modulation response at room temperature. In addition, experiments studying the dynamic response of 1.3 /spl mu/m InGaAs QDs we show that electron-hole relaxation can also be strongly temperature sensitive in the self-organized QDs.