Radiation characteristics of injection lasers based on vertically coupled quantum dots (original) (raw)
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Low-threshold injection lasers based on vertically coupled quantum dots
Journal of Crystal Growth, 1997
We have fabricated and studied injection lasers based on vertically coupled quantum dots (VECODs). VECODs are self-organized during successive deposition of several sheets of (In,Ga)As quantum dots separated by thin GaAs spacers. VECODs are introduced in the active region of a GaAs-A1GaAs GRIN SCH lasers. Increasing the number of periods (N) in the VECOD leads to a remarkable decrease in threshold current density ( ~ 100 A/cm 2 at 300 K for N = 10). Lasing proceeds via the ground state of the quantum dots (QD) up to room temperature. Placing the QD array into an external AIGaAs--GaAs quantum well allows us to extend the range of thermal stability of threshold current density (To = 350 K) up to room temperature. Using (In,Ga)As-(A1,Ga)As VECODs in combination with high temperature growth of emitter and waveguide layers results in further reduction of threshold current density (60-80 A/cm 2, 300 K) and increase in internal quantum efficiency (70%). Room temperature continuous wave operation (light output 160 mW per mirror) and lasing via the states of QDs up to I = (6-7) Ith have been demonstrated.
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.
InAs/InGaAs/GaAs quantum dot lasers of 1.3 μm range with enhanced optical gain
Journal of Crystal Growth, 2003
Near-1.3-mm lasers based on multiple layers (2, 5 and 10) of InAs/InGaAs/GaAs quantum dots with high performance have been grown by molecular beam epitaxy. A record differential efficiency as high as 88% was achieved in laser based on 10 QD layers. Threshold current density of 100-150 A/cm 2 and differential efficiency of 75-80% were achieved simultaneously in the same device. Characteristic temperature of 150 K in 20-501C temperature range was demonstrated for the laser based on 5 QD layers. A steep increase in internal loss with decreasing cavity length was found to limit the highest mirror loss possible for ground state lasing. r
MBE growth and characterisation of InGaAs quantum dot lasers
Materials Science and Engineering: B, 2000
High quality self-assembled InGaAs quantum dots have been formed on GaAs by molecular beam epitaxy via Stranski-Krastonov growth mode, and have been employed to produce quantum dot lasers with reasonably good properties. The effects of growth conditions, substrate misorientation, and doping in quantum dots on the characteristics of quantum dots and quantum dot lasers are presented. It has been shown that higher density of quantum dots is obtained under higher As flux because the diffusion length of Ga adatoms is reduced. Higher degree of substrate misorientation also leads to higher density of quantum dots since the kinks on the surface have similar effect on the diffusion of cations. It is also found that doping in the quantum dots plays an important role in the performance of quantum dot lasers. Room temperature continuous wave operation has been achieved on Be-doped quantum dot lasers. Under pulse operation, characteristic temperature as high as 121 K between 20 and 70°C has been obtained.
(In,Ga)As/GaP electrical injection quantum dot laser
Applied Physics Letters, 2014
The paper reports on the realization of multilayer (In,Ga)As/GaP quantum dot (QD) lasers grown by gas source molecular beam epitaxy (GSMBE). The QDs have been embedded in (Al,Ga)P/GaP waveguide structures. Laser operation at 710 nm is obtained for broad area laser devices with a
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.