Long-wavelength lasing from multiply stacked InAs/InGaAs quantum dots on GaAs substrates

An InAs quantum dot (QD) array covered by a thin InGaAs layer was used as t he active region of diode lasers grown by molecular beam epitaxy on GaAs su bstrates. The wavelength of the ground-state transition in such heterostruc tures is in the 1.3 mu m range. In the laser based on the single layer of Q Ds, lasing proceeds via the excited states due to insufficient gain of the ground level. Stacking of three QD planes prevents gain saturation and resu lts in a low threshold (85 A/cm(2) in broad-area 1.9-mm-long stripe) long-w avelength (1.25 mu m) lasing at room temperature via the QD ground state wi th relatively high differential efficiency (> 50%). (C) 1999 American Insti tute of Physics. [S0003-6951(99)05239-0].