Activation energy study of electron transport in high performance short wavelengths quantum cascade lasers

Pflügl, C.; Diehl, Laurent; Lyakh, Arkadiy; Wang, Qi Jie; Maulini, Richard; Tsekoun, Alexei; Patel, C. K. N.; Wang, Xiaojun; Capasso, Federico

doi:10.1364/oe.18.000746

Cited by 20 publications

(10 citation statements)

References 18 publications

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“…Fortunately, the same structure was studied in Ref. 46, and good agreement with experiment was found when τ 4g;inelastic ¼ 1.1 ps and τ 4g;elastic ¼ 1.5 ps. [The elastic part is primarily due to interface-roughness (IFR) scattering.]…”

Section: Resultsmentioning

confidence: 52%

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Design considerations for λ ∼ 3.0- to 3.5-μm-emitting quantum cascade lasers on metamorphic buffer layers

et al. 2017

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Design considerations for λ ∼ 3.0-to 3.5-μm-emitting quantum cascade lasers on metamorphic buffer layers," Opt. Eng.Abstract. Quantum cascade lasers (QCLs) that employ metamorphic buffer layers as substrates of variable lattice constant have been designed for emission in the 3.0-to 3.5-μm wavelength range. Theoretical analysis of the active-region (AR) energy band structure, while using an 8-band k • p model, reveals that one can achieve both effective carrier-leakage suppression as well as fast carrier extraction in QCL structures of relatively low strain. Significantly lower indium-content quantum wells (QWs) can be employed for the AR compared to QWs employed for conventional short-wavelength QCL structures grown on InP, which, in turn, is expected to eliminate carrier leakage to indirect-gap valleys (X, L). An analysis of thermo-optical characteristics for the complete device design indicates that high-Al-content AlInAs cladding layers are more effective for both optical confinement and thermal dissipation than InGaP cladding layers. An electroluminescence-spectrum full-width half-maximum linewidth of 54.6 meV is estimated from interface roughness scattering and, by considering both inelastic and elastic scattering, the threshold-current density for 3.39-μm-emitting, 3-mm-long back-facet-coated QCLs is projected to be 1.40 kA∕cm 2 .

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Section: Resultsmentioning

confidence: 52%

“…First of all, for η inj;tot , we consider a typical η inj value of 0.97, and for η p we take 0.85, since those devices had strong carrier leakage as evidenced by a low T 1 value of 140 K 46 which we have shown 38 to correspond to η p ≈ 0.85 for conventional 4.6-to 4.7-μm-emitting QCLs. Then η inj;tot ¼ 0.82.…”

Section: Resultsmentioning

confidence: 99%

Design considerations for λ ∼ 3.0- to 3.5-μm-emitting quantum cascade lasers on metamorphic buffer layers

et al. 2017

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“…2 These low values for both T 0 and T 1 are indirectly attributable to the small energy differential, δE = 150 to 250 meV, between the upper laser level and the top of the exit barrier. 3,4 In turn, the maximum wallplug efficiency η wp,max 0091-3286/2010/$25.00 C 2010 SPIE in cw operation at RT, for light emitted from the front facet of devices with high-reflectivity-coated back facets, has typical values 5,6 of ≈12%, far short of theoretically predicted limits 7 of ≈28% at λ ≈ 4.6 μm. In contrast, at cryogenic temperatures (40 to 80 K), where thermally activated electron leakage is negligible, maximum pulsed wallplug efficiency values as high as 50% have been achieved, 8,9 in close agreement with the theoretically predicted upper limit 10 of ≈60% at λ ≈ 4.6 μm and 80-K heatsink temperature.…”

Section: Introductionmentioning

confidence: 83%

Electron leakage and its suppression via deep-well structures in 4.5- to 5.0-μm-emitting quantum cascade lasers

et al. 2010

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The equations for threshold-current density J th and external differential quantum efficiency η d of quantum cascade lasers (QCLs) are modified to include electron leakage and the electron-backfilling term corrected to take into account hot electrons in the injector. We show that by introducing both deep quantum wells and tall barriers in the active regions of 4.8-μm-emitting QCLs, and by tapering the conduction-band edge of both injector and extractor regions, one can significantly reduce electron leakage. The characteristic temperatures for J th and η d , denoted by T 0 and T 1 , respectively, are found to reach values as high as 278 and 285 K over the 20 to 90 • C temperature range, which means that J th and η d display ≈ 2.3 slower variation than conventional 4.5-to 5.0-μm-emitting, high-performance QCLs over the same temperature range. A model for the thermal excitation of hot injected electrons from the upper laser level to the upper active-region energy states, wherefrom some relax to the lower active-region states and some are scattered to the upper miniband, is used to estimate the leakage current. Estimated T 0 values are in good agreement with experiment for both conventional QCLs and deep-well QCLs. The T 1 values are justified by increases in both electron leakage and waveguide loss with temperature.

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“…It is relatively difficult to make a quantification of thermally activated leakages in QCLs due to the lack of direct measurements. In fact, the leakages issue was extensively studied in mid-infrared QCLs relying on indirect measurement ways 16 , 17 . Some previous studies also point out its possible effects on the performance of THz-QCLs 18 , but mainly focus on the leakages flowing over low-barrier into the continuum.…”

Section: Introductionmentioning

confidence: 99%

Leakages suppression by isolating the desired quantum levels for high-temperature terahertz quantum cascade lasers

Wang

Lin

Chen

et al. 2021

Sci Rep

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The key challenge for terahertz quantum cascade lasers (THz-QCLs) is to make it operating at room-temperature. The suppression of thermally activated leakages via high lying quantum levels is emphasized recently. In this study, we employ the advanced self-consistent method of non-equilibrium Green’s function, aiming to reveal those kinds of leakages in the commonly used THz-QCL designs based on 2-, 3- and 4-quantum well. At the high temperature of 300 K, if all the confined high lying quantum levels and also the continuums are included within three neighboring periods, leakages indeed possess high fraction of the total current (21%, 30%, 50% for 2-, 3- and 4-quantum well designs, respectively). Ministep concept is introduced to weaken those leakage channels by isolating the desired levels from high lying ones, thus the leakages are well suppressed, with corresponding fractions less than 5% for all three designs.

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Activation energy study of electron transport in high performance short wavelengths quantum cascade lasers

Cited by 20 publications

References 18 publications

Design considerations for λ ∼ 3.0- to 3.5-μm-emitting quantum cascade lasers on metamorphic buffer layers

Design considerations for λ ∼ 3.0- to 3.5-μm-emitting quantum cascade lasers on metamorphic buffer layers

Electron leakage and its suppression via deep-well structures in 4.5- to 5.0-μm-emitting quantum cascade lasers

Leakages suppression by isolating the desired quantum levels for high-temperature terahertz quantum cascade lasers

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