Epitaxial growth of quantum-dot heterostructures on metamorphic buffers

Recent achievements in self-organized quantum dots (QDs) have demonstrated their potential for long-wavelength laser applications. However, the wavelength of QD structures pseudomorphically grown on GaAs substrate is typically not longer than 1.3 μm. In this work we study a novel approach for extension of the spectral range of GaAs-based diode lasers up to 1.5 μm. We use a sensitivity of QD emission to the band gap energy of surrounding matrix. The method is based on formation of a QD array inside a metamorphic InGaAs epilayer. Growth regimes of metamorphic buffer that enable mirror-like surface morphology in combination with effective dislocation trapping are discussed. Structural and optical properties of metamorphic InAs/InGaAs QDs are presented. It is shown that the wavelength of QD emission can be controllably tuned in the 1.37-1.58 μm range by varying the composition of metamorphic InGaAs matrix. Details of formation, fabrication, and characterization of metamorphic-based diode lasers are also presented. We demonstrate a lasing wavelength as long as 1.48 μm in the 20-80 °C temperature interval. The minimum threshold current density is 800 A/cm 2 at RT. The external differential efficiency and pulsed power maximum exceed 50% and 7 W, respectively.