Reduction of the threshold current density of GaAs/AlGaAs quantum cascade lasers by optimized injector doping and growth conditions

Höfling, Sven; Kallweit, R.; Seufert, Jochen; Koeth, Johannes; Reithmaier, J.P.; Forchel, A.

doi:10.1016/j.jcrysgro.2004.12.096

Cited by 24 publications

(17 citation statements)

References 12 publications

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“…The mirror losses α m =α m,c = ln(R)/2L, where R=0.27 is the uncoated mirror reflectivity. Taking experimentally determined waveguide losses α w equal to 30cm -1 , the confinement factor Γ=0.27 and the effective refractive index n=3.27 [10] as well as λ=9.5µm, τ 32 =2.1ps and γ 32 =16meV, we get J th for the 1.5-mm-long device equal to ≈7kA/cm 2, which is basically what we observe experimentally. The possible reason for high internal losses is not optimized injector doping.…”

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confidence: 78%

Room temperature AlGaAs/GaAs quantum cascade lasers

Bugajski¹

2011

Photon. Lett. Poland

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Abstract-The room temperature (293K), pulsed mode operation of a GaAs-based quantum cascade laser (QCL) is reported. This has been achieved by the use of GaAs/Al 0.45 Ga 0.55 As heterostructure. Its design follows an "anticrossed-diagonal" scheme. The QCL structures were grown by MBE in a Riber Compact 21T reactor. The double trench lasers were fabricated using standard processing technology, i.e., wet etching and Si 3 N 4 for electrical insulation. Double plasmon confinement with Al-free waveguide has been used to minimize absorption losses. High operating temperatures have been achieved by careful optimization of growth technology and using metallic high reflectivity facet coating on the back facet of the laser.

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confidence: 78%

Room temperature AlGaAs/GaAs quantum cascade lasers

Bugajski¹

2011

Photon. Lett. Poland

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“…45 The fluxes used for the waveguide ͓V/III beam equivalent pressure ͑BEP͒ ratio of 35͔ and the active region layers ͑V/III BEP ratio of 50 for GaAs layers, correspondingly less for AlGaAs layers͒ result in high-quality layers with smooth surfaces and low defect densities. Layer structures grown under these conditions exhibit threshold current densities of 2.9 kA/ cm 2 ͑8.0 kA/ cm 2 ͒ at 80 K ͑240 K͒ and maximum operation temperatures of around room temperature.…”

Section: Device Fabrication and Characterizationmentioning

confidence: 99%

“…40,41 The doping level in the active region is an important parameter with particular influence on the dynamic working range of QCLs. Until now, very few experimental investigations have been presented including the influence of the injector doping on InP-based [42][43][44] and GaAs-based [45][46][47][48] QCL threshold currents.…”

Section: Introductionmentioning

confidence: 99%

Influence of doping density on electron dynamics in GaAs∕AlGaAs quantum cascade lasers

Jovanović

Höfling

Indjin

et al. 2006

Journal of Applied Physics

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A detailed theoretical and experimental study of the influence of injector doping on the output characteristics and electron heating in midinfrared GaAs/ AlGaAs quantum cascade lasers is presented. The employed theoretical model of electron transport was based on a fully nonequilibrium self-consistent Schrödinger-Poisson analysis of the scattering rate and energy balance equations. Three different devices with injector sheet doping densities in the range of ͑4 -6.5͒ ϫ 10 11 cm -2 have been grown and experimentally characterized. Optimized arsenic fluxes were used for the growth, resulting in high-quality layers with smooth surfaces and low defect densities. A quasilinear increase of the threshold current with sheet injector doping has been observed both theoretically and experimentally. The experimental and calculated current-voltage characteristics are in a very good agreement. A decrease of the calculated coupling constant of average electron temperature versus the pumping current with doping level was found.

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“…Although the exact level of active region thickness/com− position inaccuracy that results disastrously is not obvious, one may conclude that for MIR emitters it may be not much more than~4% of layer thickness [1] and for FIR emitters it may be even less [2]. We know by our experience that no GaAs/AlGaAs MIR QCL structure with active region thick− ness inaccuracy bigger than~7% yield lasing devices or at best they lase at temperatures of few tens of degrees lower than for the proper constructions.…”

Section: Introductionmentioning

confidence: 99%

“…There is a wide agreement that changes of the injector doping level in the range of few ten per cents are crucial [1,[4][5][6][7][8][9], though variations of about 10% may be acceptable [2,10].…”

Section: Introductionmentioning

confidence: 99%

Multi-step interrupted-growth MBE technology for GaAs/AlGaAs (∼9.4 μm) room temperature operating quantum-cascade lasers

Kosiel

Kubacka-Traczyk

Sankowska

et al. 2012

Opto-Electronics Review

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In order to adjust the highly controllable and optimum growth conditions, the multi-step interrupted-growth MBE processes were performed to deposit a series of GaAs/Al0.45Ga0.55As QCL structures. The additional calibrations of MBE system were carried out during the designed growth interruptions. This solution was combined with a relatively low growth rate of active region layers, in order to suppress the negative effects of elemental flux instabilities. As a result, the fabricated QCL structures have yielded devices operating with peak optical power of ∼12 mW at room temperature. That is a better result than was obtained for comparable structures deposited with a growth rate kept constant, and with the only initial calibrations performed just before the epitaxy of the overall structure.

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Reduction of the threshold current density of GaAs/AlGaAs quantum cascade lasers by optimized injector doping and growth conditions

Cited by 24 publications

References 12 publications

Room temperature AlGaAs/GaAs quantum cascade lasers

Room temperature AlGaAs/GaAs quantum cascade lasers

Influence of doping density on electron dynamics in GaAs∕AlGaAs quantum cascade lasers

Multi-step interrupted-growth MBE technology for GaAs/AlGaAs (∼9.4 μm) room temperature operating quantum-cascade lasers

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