Intersubband carrier scattering in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>n</mml:mi></mml:math>- and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>p</mml:mi><mml:mtext>−</mml:mtext><mml:mi mathvariant="normal">Si</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">Si</mml:mi><mml:mi mathvariant="normal">Ge</mml:mi></mml:mrow></mml:math>quantum wells with diffuse interfaces

Valavanis, Alexander; Ikonić, Z.; Kelsall, R. W.

doi:10.1103/physrevb.77.075312

Cited by 23 publications

(37 citation statements)

References 31 publications

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“…We used a semiclassical time-independent perturbation theoretical approach, including interface roughness (IR), alloy disorder (AD), deformation potential electron-phonon interactions (EP), acoustic phonon (AC) and ionised impurity (II) interactions. [11] For all our calculations, we set the lattice temperature to 4 K. The carrier temperature was set to 24 K which yields scattering rates in good agreement with pumpprobe spectroscopy measurements on double well systems. [17] As modulation doping of SiGe-based heterostructures may be poor, [9] doping was spread evenly throughout each system at a concentration of 10 16 cm −3 .…”

Section: Transport Modelmentioning

confidence: 96%

“…[8] In reality however, diffuse Ge profiles may result from processes such as surface segregation during growth, [9] or by annealing. [10] Having established that this leads to significant changes in the subband spacing and scattering rates in QWs, [11] we now turn to the specific issue of barrier degradation in QC lasers.…”

Section: Introductionmentioning

confidence: 99%

“…In the following sections, we briefly summarise our semiclassical transport model and the general effect of interdiffusion upon semiconductor bandstructure. We then define figures of merit for tolerance to Ge interdiffusion and use the method proposed in our previous work [11] to investigate the degradation in barrier potential for coupled QWs in each of the material configurations discussed above.…”

Section: Introductionmentioning

confidence: 99%

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Growth variation effects in SiGe-based quantum cascade lasers

Valavanis¹,

Ikonić²,

Kelsall³

2009

J. Opt. A: Pure Appl. Opt.

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Abstract. Epitaxial growth of SiGe quantum cascade (QC) lasers has thus far proved difficult, and nonabrupt Ge profiles are known to exist. We model the resulting barrier degradation by simulating annealing in pairs of quantum wells (QWs). Using a semiclassical charge transport model, we calculate the changes in scattering rates and transition energy between the lowest pair of subbands.We compare results for each of the possible material configurations for SiGe QC lasers. The effects are most severe in n-type (001) Si-rich systems due to the large effective electron mass, and in p-type systems due to the coexistence of light-and heavy-holes.The lower effective mass and conduction band offset of (111) oriented systems minimises transition energy variation, and a large interdiffusion length (L d = 1.49 nm) is tolerated with respect to scattering rate. Ge-rich systems are shown to give the best tolerance with respect to subband separation (L d = 3.31 nm), due also to their low effective mass.

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Section: Transport Modelmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Growth variation effects in SiGe-based quantum cascade lasers

Valavanis¹,

Ikonić²,

Kelsall³

2009

J. Opt. A: Pure Appl. Opt.

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“…Both processes change the electronic behaviour of a system by narrowing the QWs and degrading the barriers of QWs. In such interdiffused or inter-mixed QW structures with smooth interface profiles, significant changes in the sub-band spacing and carrier scattering rates in a Si/SiGe QW system [6], were predicted.…”

Section: Introductionmentioning

confidence: 99%

“…Their most spectacular applications are quantum well IR photodetectors [3] and the quantum cascade (QC) lasers [4], that relies on the cascaded intersub-band transitions and resonant tunneling between adjacent QWs. These devices are made with epitaxially grown GaAs/AlGaAs, InGaAs/AlInAs, GaN/AlGaN [1,5]], and Si/SiGe [6] systems. With the recent development on semiconductor device growth technology, multi-barrier quantum well structures are becoming the basic building blocks of modern semiconductor devices, such as resonant tunneling diodes (RTD) [7], high-speed light modulators [8,9], wavelength tunable lasers [10,11], far-infrared and THz lasers [12], quantum cascade (QC) lasers [4,13], etc.…”

Section: Introductionmentioning

confidence: 99%

Asymmetric double quantum wells with smoothed interfaces

Gavryushin

2012

Open Physics

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Abstract:We have derived and analyzed the wavefunctions and energy states for an asymmetric double quantum well (ADQW), broadened due to interdiffusion or other static interface disorder effects, within a known discreet variable representative approach for solving the one-dimensional Schrodinger equation. The main advantage of this approach is that it yields the energy eigenvalues, and the eigenvectors, in semiconductor nanostructures of different shapes as well as the strengths of the optical transitions between them. The behaviour of ADQW states for the different mutual widths of coupled wells, for the different degree of broadening, and under increasing external electric field is investigated. We have found that interface broadening effects change and shift energy levels, not monotonously, but the resonant conditions near an energy of sub-band coupling regions do not strongly distort. Also , it is shown that an external electric field may help to achieve resonant conditions for inter-sub-band inverse population by intrawell emission of LO-phonons in diffuse ADQW. PACS

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Carrier scattering

2016

Quantum Wells, Wires and Dots

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So far, the present work has considered only the static behaviour of carriers in nanostructures. In other words, the states that carriers could occupy within a structure have been calculated, along with the Fermi-Dirac distributions of carriers in thermal equilibrium. However, the equilibrium distribution of carriers is broken in real heterostructure devices (e.g. by the injection of an electric current or an optical 'pump'), and it is therefore important to consider the dynamic behaviour of carriers in such systems in order to predict their distribution accurately.In principle, a complete model of the behaviour of a carrier within a heterostructure could be obtained by finding a Hamiltonian that describes all possible interactions between the carrier and its surroundings, and then solving the time-dependent Schrödinger equation to observe the evolution of the carrier wave function over time. However, this is a formidable computational task, which is further complicated by the random nature of many of the interactions (e.g. randomly distributed impurities). To simplify the problem, carrier dynamics may be approximated by two distinct types of process: coherent processes in which wave functions evolve smoothly between their initial and final states; and incoherent, scattering processes. The latter are the focus of this chapter, and are defined as random, infrequent but very rapid events that transfer a carrier between two states. This could be caused by interactions between carriers and any kind of perturbing potential, including other carriers, impurities, and defects in the heterostructure, or with lattice vibrations (phonons) and photons.Since scattering is assumed to be infrequent, the system can be assumed to stabilise to its static, unperturbed state between events. As such, the eigenstates of the unperturbed system can be calculated (as in Chapters 2 and 3) independently from the scattering dynamics. The very rapid nature of scattering events introduces a further simplification: carriers effectively 'hop' instantaneously from one state to another, and the only necessary task is to compute the rate of scattering (i.e. the number of events per second) for any combination of initial and final states, which is the focus of this chapter. After determining these scattering rates for appropriate interaction processes, the results are used in Chapter 12 to compute the populations of states and current density in devices.

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Intersubband carrier scattering inn- andp−Si∕SiGequantum wells with diffuse interfaces

Cited by 23 publications

References 31 publications

Growth variation effects in SiGe-based quantum cascade lasers

Growth variation effects in SiGe-based quantum cascade lasers

Asymmetric double quantum wells with smoothed interfaces

Carrier scattering

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