Enhanced modulation bandwidth (20 GHz) of In/sub 0.4/Ga/sub 0.6/As-GaAs self-organized quantum-dot lasers at cryogenic temperatures: role of carrier relaxation and differential gain

Measurements of the threshold current, slope efficiency and optical modulation characteristics of self-assembled InGaAs-GaAs quantum-dot lasers have been made in the temperature range of 20-200 K in order to understand the carrier dynamics in these devices. The dc characteristics of these devices showed a region of almost temperature independent threshold current up to 85 K (T/sub 0/=670 K) with a maximum slope efficiency at 150 K. The maximum measured bandwidth increased from 5 GHz at room temperature to 20 GHz at 80 K. This is consistent with the bandwidth being limited by carrier relaxation time through electron-hole scattering.