Role of interface roughness in the transport and lasing characteristics of quantum-cascade lasers

Khurgin, Jacob B.; Dikmelik, Yamaç; Liu, Peter Q.; Hoffman, Anthony J.; Escarra, Matthew D.; Franz, Kale J.; Gmachl, Claire F.

doi:10.1063/1.3093819

Cited by 78 publications

(32 citation statements)

References 13 publications

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“…4 shows the effect of varying IFR parameters on the peak-to-valley (PVR) ratio calculated by the DM model. Interface roughness has been shown to have a significant effect on transport in unipolar devices 59 and can suppress gain almost completely in tall-barrier QCLs.…”

Section: Resultsmentioning

confidence: 99%

Coherent vertical electron transport and interface roughness effects in AlGaN/GaN intersubband devices

Grier

Valavanis

Edmunds

et al. 2015

Journal of Applied Physics

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We investigate electron transport in epitaxially grown nitride-based resonant tunneling diodes (RTDs) and superlattice sequential tunneling devices. A density-matrix model is developed, and shown to reproduce the experimentally measured features of the current-voltage curves, with its dephasing terms calculated from semi-classical scattering rates. Lifetime broadening effects are shown to have a significant influence in the experimental data. Additionally, it is shown that the interface roughness geometry has a large effect on current magnitude, peak-to-valley ratios and misalignment features; in some cases eliminating negative differential resistance entirely in RTDs. Sequential tunneling device characteristics are dominated by a parasitic current that is most likely to be caused by dislocations; however, excellent agreement between the simulated and experimentally measured tunneling current magnitude and alignment bias is demonstrated. This analysis of the effects of scattering lifetimes, contact doping and growth quality on electron transport highlights critical optimization parameters for the development of III-nitride unipolar electronic and optoelectronic devices. V C 2015 AIP Publishing LLC. [http://dx

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Section: Resultsmentioning

confidence: 99%

Coherent vertical electron transport and interface roughness effects in AlGaN/GaN intersubband devices

Grier

Valavanis

Edmunds

et al. 2015

Journal of Applied Physics

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“…15 Here, to estimate the effect of inter-and intra-subband scattering induced by asymmetric interfaces on our device performance under different polarities, we follow Ref. 14:…”

Section: Simulation Resultsmentioning

confidence: 99%

Importance of growth direction in mid-infrared quantum cascade lasers

Bouzi

Chiu

Deutsch

et al. 2014

Journal of Applied Physics

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We report on the effect of growth direction on the performance of mid-infrared Quantum Cascade lasers. The design used has a symmetric active core, capable of operating under both negative and positive polarities, which allows to test for residual growth asymmetries such as interface roughness and dopant migration. Calculations of scattering lifetimes from interface roughness and ionized impurities suggest a dominant contribution from the former, with devices biased positively averaging $15% larger broadening and $50% shorter upper state lifetime than negatively biased devices. Experimental results for positively biased devices show at least 30% larger broadening and 35% lower electroluminescence peak intensity than those biased negatively, in good agreement with the modeling results. V C 2014 AIP Publishing LLC. [http://dx

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“…Previous DM models of III-V BTC QCLs have reproduced experimental results by including only the upper laser level (ULL) and a subset of miniband states in their basis set, of which one is designated as the injector. 16 However, in practice multiple subbands may contribute significantly to interperiod tunneling in BTC QCLs. Our extended non-RWA DM model avoids the need for a priori selection of the optically-coupled transition and the injector subband, allowing us to use the semi-automated design approach described in Ref.…”

Section: Simulation Resultsmentioning

confidence: 99%

“…Although semiclassical scattering-transport models can give good agreement with experimental results, 1,14 they neglect tunneling across barriers, and can predict unrealistically large spikes in current density and gain when electrons scatter between spatially-extended subbands. 15 By contrast, simplified density matrix (DM) models [15][16][17][18][19][20][21] account for tunneling, in addition to scattering, and include the effect of the optical field on the electron dynamics.…”

Section: -11mentioning

confidence: 99%

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Extended density-matrix model applied to silicon-based terahertz quantum cascade lasers

et al. 2012

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Silicon-based terahertz quantum cascade lasers (QCLs) offer potential advantages over existing III-V devices. Although coherent electron transport effects are known to be important in QCLs, they have never been considered in Si-based device designs. We describe a density matrix transport model that is designed to be more general than those in previous studies and to require less a priori knowlege of electronic bandstructure, allowing its use in semi-automated design procedures. The basis of the model includes all states involved in interperiod transport, and our steady-state solution extends beyond the rotating-wave approximation by including DC and counter-propagating terms. We simulate the potential performance of bound-to-continuum Ge/SiGe QCLs and find that devices with 4-5-nm-thick barriers give the highest simulated optical gain. We also examine the effects of interdiffusion between Ge and SiGe layers; we show that if it is taken into account in the design, interdiffusion lengths of up to 1.5 nm do not significantly affect the simulated device performance.

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Role of interface roughness in the transport and lasing characteristics of quantum-cascade lasers

Cited by 78 publications

References 13 publications

Coherent vertical electron transport and interface roughness effects in AlGaN/GaN intersubband devices

Coherent vertical electron transport and interface roughness effects in AlGaN/GaN intersubband devices

Importance of growth direction in mid-infrared quantum cascade lasers

Extended density-matrix model applied to silicon-based terahertz quantum cascade lasers

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