1.5 micron InAs quantum dot lasers based on metamorphic InGaAs/GaAs heterostructures.
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1.5 micron InAs quantum dot lasers based on metamorphic InGaAs/GaAs heterostructures. V.M.Ustinov, A.E.Zhukov, A.R.Kovsh, N.A.Maleev, S.S.Mikhrin, A.P.Vasil’ev, E.V.Nikitina, E.S.Semenova, N.V.Kryzhanovskaya, Yu.G.Musikhin, Yu.M.Shernyakov, M.V.Maximov, N.N.Ledentsov1, D.Bimberg1, Zh.I.Alferov Ioffe Physico-Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg, Russia 1 Institut für Festkörperphysik, Technische Universität Berlin, PN5-2, Hardenbergst. 36, D-10623 Berlin, Germany ABSTRACT 1.5 micron range emission has been realized using the InAs quantum dots embedded into the metamorphic InGaAs layer containing 20% of InAs grown by MBE on a GaAs substrate. Growth regimes were optimized to reduce significantly the density of dislocations propagating into the active layer from the lattice mismatched interface. 2 mm long InGaAs/InGaAlAs lasers with 10 planes of quantum dots in the active region showed threshold current density about 1.4 kA/cm2 with the external differential efficiency as high as 38%. Lasing wavelength depends on the optical loss being in the 1.44-1.49 micron range at room temperature. On increasing the temperature the wavelength reaches 1.515 micron at 85C while the threshold current characteristic temperature of 55-60K was estimated. High internal quantum efficiency (ŋ>60%) and low internal losses (α=3-4 cm-1) were realized. Maximum room temperature output power in pulsed regime as high as 5.5 W for 100 micron wide stripe was demonstrated. Using the same concept 1.3 micron InGaAs/InGaAlAs quantum well lasers were fabricated. The active region contained quantum wells with high (~40%) indium content which was possible due to the intermediate InGaAs strain relaxation layer. 1 mm stripe lasers showed room temperature threshold current densities about 3.3 kA/cm2 (λ=1.29 micron) and 400 A/cm2 at 85K. Thus, the use of metamorphic InGaAs layers on GaAs substrate is a very promising approach for increasing the emission wavelength of GaAs based lasers.
INTRODUCTION Current strong interest in long wavelength semiconductor diode lasers on GaAs substrates [1] is due to their datacom and telecom applications. High performance 1.3 µm InAs quantum dot (QD) lasers and vertical-cavity surface emitting lasers (VCSELs) grown on GaAs substrates have been reported [2], however, 1.5 micron range still remains a challenge. InGaAsN [3], and InGaAsNSb [4] quantum well lasers emitting at 1.5 µm have been published but their performance is still inferior to 1.3 µm devices. Until now, however, no QD lasing in this spectral range was reported, presumably, due to the high defect density in 1.5 µm InAs-GaAs structures. In the present work we suggest InAs QDs embedded into an InGaAs metamorphic layer as a new active medium for GaAs based long wavelength semiconductor lasers. We show that careful optimization of MBE growth regimes allows us to drastically decrease the amount of dislocations propagating into the device active layer and thereby to improve laser characteristics. This approach looks to be very
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