(In,Ga)As/GaP electrical injection quantum dot laser (original) (raw)
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Journal of Crystal Growth, 1999
Injection lasers based on self-organized (In,Ga)As/(Al,Ga)As quantum dots (QD) su!er from the gain saturation due to the limited amount of QD states participating in lasing. In the present work, we demonstrate the direct increase in the areal density of (In,Ga)As QDs. We used an array of (In,Al)As QDs demonstrating considerably higher density than Al-free QDs as nucleation centers for the (In,Ga)As QD formation. Finally, composite vertically coupled (In,Al)As/(In,Ga)As QDs with increased areal density are formed, which is con"rmed by photoluminescence and TEM. Using the denser array of (In,Al)As/(In,Ga)As QDs in the active region of injection laser leads to the increase in modal gain, reduction in threshold current density at high mirror loss, and increase in maximum output power.
High-power continuous-wave operation of a InGaAs/AlGaAs quantum dot laser
Journal of Applied Physics, 1998
A 1 W continuous-wave laser operation via the ground state of vertically coupled InGaAs quantum dots ͑VCQDs͒ in an AlGaAs matrix is demonstrated. VCQDs are directly revealed in transmission electron microscopy images of the laser structure. Ninety-six percent internal quantum efficiency is realized. The laser gain maximum shifts significantly with drive current towards higher photon energies in agreement with the relatively broad size distribution of VCQDs. © 1998 American Institute of Physics. ͓S0021-8979͑98͒01210-9͔
Comparison of InAs quantum dot lasers emitting at 1.55 µm under optical and electrical injection
Semiconductor Science and Technology, 2005
InAs/InGaAsP/InP(113)B quantum-dots are studied as active mediums for laser structures emitting near 1.55 µm under optical and electrical injection. In order to precisely tune the emission wavelength of QDs, the double cap growth procedure is used. Laser emission on the ground states is obtained under optical pumping at room temperature. On equivalent structures doped for electrical injection, laser emission is also observed at low temperatures up to 200 K. The difference between the optical and electrical pumping is ascribed to low carrier injection efficiency due to the presence of a 3 nm InP hole blocking barrier at each quantum dot layer which is inherent to the double cap growth procedure. Room temperature laser emission has been reached when the InP first cap layer is substituted by a quaternary GaInAsP (1.18 µm gap) layer in the double cap growth procedure. The threshold current density of the new structure with QD capped only by quaternary is as low as 840 A cm −2 at room temperature.
Radiation characteristics of injection lasers based on vertically coupled quantum dots
Superlattices and Microstructures, 1997
We have studied injection lasers based on InGaAs/GaAs vertically coupled quantum dots (QD) grown by molecular beam epitaxy. The threshold current density decreases by one order of magnitude down to 90 A cm −2 (300 K) with an increase of the number of QD stacks (N ) up to 10. For N ≥ 3 lasing occurs via the QD ground state up to room temperature. Differential efficiency increases with N up to 50%. No change in range of high temperature stability of threshold current density (J th ) was observed, while the characteristic temperature (T 0 ) measured at 300 K increases from 60 to 120 K. Using InGaAs-AlGaAs QD with higher localization energy allowed us to decrease J th down to 60 A cm −2 and to increase the differential efficiency up to 70%.
Quantum dot lasers: breakthrough in optoelectronics
Thin Solid Films, 2000
Semiconductor heterostructures with self-organized quantum dots (QDs) have experimentally exhibited properties expected for zerodimensional systems. When used as active layer in the injection lasers, these advantages help to strongly increase material gain and differential gain, to improve temperature stability of the threshold current, and to provide improved dynamic properties. Molecular beam epitaxy (MBE) represents a developed technology well suited for fabrication of self-organized QDs. Optimization of deposition parameters can ensure that the self-organized islands are small (,10 nm), have a similar size and shape and form dense arrays. Saturation material gain is as high as 150000 cm 21 compared with QW values of about 3000 cm 21. Maximum differential gain reported for QD lasers approaches 10 212 cm 2 and exceeds the QW laser values by about three orders of magnitude. Direct observation of relaxation oscillations reveals present cutoff frequencies close to 10 GHz. High internal (.96%) and differential (70%) ef®ciencies at 300 K are realized. Using the novel concept of electronically-coupled QDs and oxide-de®ned 10 mm apertures, CW lasing with J th 180 A/cm 2 , is realized in surface-emitting QD lasers (300 K). Wall-plug ef®ciencies are up to 16%. Total currents as low as 68 mA are measured for 1mm apertures. GaAs-based lasers for the 1.3 mm range with low J th (65 A/cm 2) at room temperature (RT) are realized using InAs/InGaAs/GaAs QDs obtained by activated spinodal decomposition. In stripes the lasing occurs via the QD ground state (J th 90 A/cm 2) for cavity lengths L. 1 mm (uncoated). Differential ef®ciency is 55% and internal losses are 1.5 cm 21. A characteristic temperature near RT is 160 K. 3W CW operation at RT is achieved. The recent progress in lasers based on self-organized MBE QDs already made it possible to fabricate devices with dramatically improved characteristics as compared to recent QW devices for the most important commercial applications.
High-performance InAs/GaAs quantum dot laser with dot layers grown at 425 oC
Chinese Optics Letters, 2013
We investigate InAs/GaAs quantum dot (QD) lasers grown by gas source molecular beam epitaxy with different growth temperatures for InAs dot layers. The same laser structures are grown, but the growth temperatures of InAs dot layers are set as 425 and 500 • C, respectively. Ridge waveguide laser diodes are fabricated, and the characteristics of the QD lasers are systematically studied. The laser diodes with QDs grown at 425 • C show better performance, such as threshold current density, output power, internal quantum efficiency, and characteristic temperature, than those with QDs grown at 500 • C. This finding is ascribed to the higher QD density and more uniform size distribution of QDs achieved at 425 • C.
InGaN/GaN self-organized quantum dot lasers grown by molecular beam epitaxy
Journal of Crystal Growth, 2013
Blue-and green-emitting quantum dots have been characterized and ridge waveguide lasers incorporating such quantum dots into the active region have been realized. The laser heteroscturctures were grown by plasma assisted molecular beam epitaxy. Injected carrier lifetimes in the quantum dots have also been measured by temperature dependent and time resolved photoluminescence. A threshold current density of 930 A/cm 2 in the blue-emitting lasers was measured under pulsed bias. A tunnel injection scheme to inject holes has been incorporated in the design of the green quantum dot lasers, and a threshold current density of 945 A/cm 2 in the green-emitting lasers has been measured under pulsed bias. Slope efficiencies of 0.41 W/A and 0.25 W/A have been measured, corresponding to differential quantum efficiencies of 13.9% and 11.3%, in the blue and green lasers, respectively.