Gain and threshold characteristics of long wavelength lasers basedon InAs/GaAs quantum dots formed by activated alloy phaseseparation

摘要

Experimental and theoretical study was made of injection lasersnbased on InAs/GaAs quantum dots (QDs) formed by the activated alloynphase separation and emitting at about 1.3 Μm. Electroluminescencenand gain spectra were investigated. The maximum modal gain is measurednexperimentally using two different techniques. Threshold currentndensities as low as 22 A cm-2 per QD sheet were achieved. Anstep-like switch from ground- to excited-state transition lasing wasnobserved with an increasing cavity loss. The characteristic temperaturesnfor a sample with four cleaved sides and a 2-mm long stripe device atn300 K were 140 and 83 K, respectively. Single lateral-modencontinuous-wave (CW) operation with the maximum output power of 210 mWnwas realized. Threshold characteristics of a laser were simulated takingninto account radiative recombination in QDs, the wetting layer, and thenoptical confinement layer. The dependence of the threshold currentndensity on the cavity length was shown to be extremely sensitive to thenQD-array parameters determining the maximum gain for ground- andnexcited-state transitions and to the waveguide design. Our analysisnreveals that nonradiative recombination channels may play an importantnrole in the laser operation