Interface-roughness-induced broadening of intersubband electroluminescence in p-SiGe and n-GaInAs∕AlInAs quantum-cascade structures

Tsujino, S.; Borak, A.; Müller, E.; Scheinert, M.; Falub, C.V.; Sigg, H.; Grützmacher, Detlev; Giovannini, Marcella; Faist, Jérôme

doi:10.1063/1.1862344

Cited by 91 publications

(59 citation statements)

References 26 publications

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“…Our best fits are obtained with ∆ = 1.2-1.5 A and Λ = 40-60Å suggesting good quality interfaces. These IFR parameters are also within the range of values reported in the literature [9,11,12,18] A was also assumed by Leuliet et al in their study of GaAs/AlGaAs QCLs [13], to obtain the best agreement between theoretical and experimental total scattering rates. In all our calculations we also assume the carrier temperature T h at detection time to be related to the lattice temperature T latt according to T h = T latt +δT , where δT is a constant (i.e., T latt -independent) quantity representing the residual effects of the carrier heating produced by the laser pulse.…”

Section: Resultssupporting

confidence: 62%

“…Due to the lack of detailed experimental information on the quality of our samples interfaces, we resorted to the standard [8,12,17] procedure of treating ∆ and Λ as fitting parameters. We deduced their values from the temperature dependence of the decay time in one structure (BF1499) and then used them in the calculation of the lifetimes of the other structure (BF1500), obtaining very good agreement with our measured data, as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…A tunability with barrier width has been demonstrated previously at energies above ω opt , where lifetimes varying between 20 ps and 35 ps were deduced from electroluminescence measurements for diagonal transitions in QC structures of pSi/SiGe [6]. However the transport properties in semiconductor quantum wells have also been shown [7][8][9][10][11][12] to be strongly influenced by the quality of the interfaces. Fluctuations in the well width due to the presence of nonideal surfaces result in local fluctuations of the carriers' confinement potential, which act as a scattering potential for the 2D carrier gas.…”

Section: Introductionmentioning

confidence: 91%

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Interwell relaxation times inp−Si∕SiGeasymmetric quantum well structures: Role of interface roughness

et al. 2007

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Article:Califano, M., Vinh, N.Q., Phillips, P.J. et al. (10 more We report the direct determination of non-radiative lifetimes in Si/SiGe asymmetric quantum well structures designed to access spatially indirect (diagonal) interwell transitions between heavy-hole ground states, at photon energies below the optical phonon energy. We show both experimentally and theoretically, using a six-band k·p model and a time-domain rate equation scheme, that, for the interface quality currently achievable experimentally (with an average step height ≥ 1Å), interface roughness will dominate all other scattering processes up to about 200 K. By comparing our results obtained for two different structures we deduce that in this regime both barrier and well widths play an important role in the determination of the carrier lifetime. Comparison with recently published experimental and theoretical data obtained for mid-infrared GaAs/AlGaAs multiple quantum well systems leads us to the conclusion that the dominant role of interface roughness scattering at low temperature is a general feature of a wide range of semiconductor heterostructures not limited to IV-IV materials.PACS numbers:

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Section: Resultssupporting

confidence: 62%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 91%

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Interwell relaxation times inp−Si∕SiGeasymmetric quantum well structures: Role of interface roughness

et al. 2007

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“…The energy and linewidth of an intersubband transition are closely related to each other in optoelectronic device design. In narrow QWs, especially at low temperature, two parameters (L and V b ) also a ect the absorption/emission linewidth, which is usually governed by interface roughness scattering [8][9][10][11][12][13]. In other words, the interface roughness scattering plays the dominant role in controlling the linewidth.…”

Section: Introductionmentioning

confidence: 99%

A novel approach to the evaluation of interface roughness scattering form factor in intersubband transitions

Tiên¹,

Thảo²,

Tuan³

2014

Nanoscale Systems: Mathematical Modeling, Theory and Applications

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Abstract:We propose a modi cation of the interface roughness (IFR) scattering form factor in intersubband transitions. We properly derived a formula for the form factor for IFR scattering in terms of the integrals of the envelope wave functions. This novel form factor is more global nature than the old one (proposed by Ando) and may be suitable for a wide range of applications. In this paper, we calculate and compare the absorption linewidth with the application of the old form factor and novel one. In di erent from previous calculations, with the same surface pro le (∆, Λ), the calculation results the interface roughness scattering absorption linewidth with the application of the new form factor is greater than twice the old one. Our numerical calculations may better explain the experimental results the well-width dependence of intersubband absorption linewidth.

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“…[3][4][5] Therefore, a reduction of the linewidth requires a further optimization of the growth condition and/or the band structure that is less sensitive to the interface roughness.…”

Section: Introductionmentioning

confidence: 99%

Strategies to improve optical gain and waveguide loss in SiGe quantum cascade devices

Tsujino

Scheinert

Sigg

et al.

IEEE International Conference on Group IV Photonics, 2005. @Nd

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Strain-compensated p-type SiGe quantum cascade structures are promising candidates to realize an efficient Si-based light source. Here we report strategies to improve the optical gain and waveguide loss to develop a SiGe quantum cascade laser.Quantum cascade (QC) devices based on the SiGe hetero-structures have been studied to develop a Si-based laser in the midinfrared. Possible applications of such a device include free space communication within the atmospheric window or the detection and analysis of organic materials. In QC lasers, the light is generated by intersubband optical transitions between quantized states. Therefore, the optical transition is not restricted by the inefficient interband processes in Si-based materials. The intersubband optical gain is obtained by controlling the carrier dynamics by band engineering to achieve population inversion between designed transition states. The challenge to realize a SiGe QC laser is to optimize the optical gain that can surmount the free carrier absorption in the active layers and in the electrical contacts. From a simple analysis, we expect that the gain-to-loss ratio in SiGe QCs is inferior to the III-V semiconductor based QC's because of the factor of 3-5 larger effective mass in SiGe.The SiGe QCs studied here are p-type and consist of Si 0.2 Ge 0.8 wells and Si barriers designed to be strain-compensated to Si 0.5 Ge 0.5 virtual substrates. The samples are prepared by solid-source molecular beam epitaxy at low growth temperature. Figure 1(a) shows the bandstructure of a benchmark sample.[1-3] We analyzed the current density dependence of the electroluminescence (EL) intensity of the sample in detail and found that the maximum gain coefficient G per unit cascade cell is limited below 1 cm -1 , with the maximum injection current density of ~5 kA/cm 2 , the upper state lifetime < ~ 100 fs, and the linewidth of 40-60 meV. Here, G is primarily in competition with the loss α due to the free carrier absorption of the carriers in the active layer itself: α is estimated to be equal to ~ 20 cm -1 at the target photon energy of 200 meV with the momentum relaxation time of 10 fs and the doping concentration of 5x10 17 cm -3 for this sample. Therefore, a substantial improvement of the gain is required to surmount the free carrier loss as well as the additional loss that arises in the waveguide device especially from the electrical contact regions. Since the ratio G/α is approximately independent of the carrier concentration in our midinfrared emitters, the increase of the injection efficiency and upper state lifetime, and/or the reduction of the linewidth are required to improve the gain and to achieve the lasing.We find that the EL linewidth of our SiGe QCs is limited by the interface roughness based on the estimated roughness parameters obtained from the x-ray reflectivity measurement, the high resolution cross-sectional transmission electron microcopy, and from the analysis of the relation between the thickness and the low-temperature hall mobility in quant...

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Interface-roughness-induced broadening of intersubband electroluminescence in p-SiGe and n-GaInAs∕AlInAs quantum-cascade structures

Cited by 91 publications

References 26 publications

Interwell relaxation times inp−Si∕SiGeasymmetric quantum well structures: Role of interface roughness

Interwell relaxation times inp−Si∕SiGeasymmetric quantum well structures: Role of interface roughness

A novel approach to the evaluation of interface roughness scattering form factor in intersubband transitions

Strategies to improve optical gain and waveguide loss in SiGe quantum cascade devices

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