Control of Electron-State Coupling in Asymmetric 
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 Quantum Wells

Ciano, Chiara; Virgilio, Michele; Montanari, Michele; Persichetti, Luca; Gaspare, L. Di; Ortolani, Michele; Baldassarre, Leonetta; Zoellner, M. H.; Skibitzki, Oliver; Scalari, Giacomo; Faist, Jérôme; Paul, Douglas J.; Scuderi, M.; Nicotra, Giuseppe; Grange, Thomas; Birner, Stefan; Capellini, Giovanni; Seta, M. De

doi:10.1103/physrevapplied.11.014003

Cited by 25 publications

(42 citation statements)

References 34 publications

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“…At high magnifications ( Fig. 1c,d), STEM shows sharp and abrupt interfaces, with a broadening due to SiGe intermixing in the order of 0.8 nm [21]. The quality of the heterointerfaces is confirmed by the low value of the rootmean-square interface roughness which was estimated to be 0.18 nm by atomic probe tomography measurements performed on the same set of samples [30].…”

Section: Methodsmentioning

confidence: 77%

“…Among different samples, wt= 5.0 nm is kept constant, wL is varied between 11.3 and 16.0 nm and bt ranges between 2.3 and 5 nm. xGe has been set to 0.81 or 0.87, with the higher Ge composition describing the more pronounced SiGe intermixing for bt< 3 nm [21]. The wide well is n-doped by phosphine codeposition over a thickness t= 10 nm.…”

Section: Methodsmentioning

confidence: 99%

“…The most promising QCL design for successful lasing operation in the group-IV material platform exploits ISB transitions of electrons in the conduction-band L valleys of Ge-rich heterostructures and features, as a building block, asymmetric-coupled quantum wells (ACQWs) made of Ge layers of different thicknesses and coupled through Si(1-x)Gex barriers, typically with a Ge content x=0.77  0.85 [22,23]. This ACQW system inherently presents some of the main challenges for a future QCL development in the SiGe system [21], such as (i) achieving high structural and interface quality in strain-compensated Ge-rich heterostructures despite their large lattice mismatch with the Si substrate; (ii) control of the concentration profile of n-type dopant P atoms during the epitaxial growth and quantification of the profile broadening due to surface segregation of donors; (iii) designing of the energy of ISB transitions and engineering of electron wavefunctions with the desired degree of delocalization. As a necessary milestone on the way towards a SiGe based QCL, we investigate in this paper n-doped Ge/Si0.20Ge0.80 ACQWs grown by chemical vapor deposition (CVD), combining structural analysis techniques with THz spectroscopy as a probe of interwell coupling and level broadening due to interface roughness and ionized impurity scatterings.…”

Section: Introductionmentioning

confidence: 99%

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Intersubband Transition Engineering in the Conduction Band of Asymmetric Coupled Ge/SiGe Quantum Wells

et al. 2020

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n-type Ge/SiGe asymmetric-coupled quantum wells represent the building block of a variety of nanoscale quantum devices, including recently proposed designs for a silicon-based THz quantum cascade laser. In this paper, we combine structural and spectroscopic experiments on 20module superstructures, each featuring two Ge wells coupled through a Ge-rich tunnel barrier, as a function of the geometry parameters of the design and the P dopant concentration. Through the comparison of THz spectroscopic data with numerical calculations of intersubband optical absorption resonances, we demonstrated that it is possible to tune by design the energy and the spatial overlap of quantum confined subbands in the conduction band of the heterostructures. The high structural/interface quality of the samples and the control achieved on subband hybridization are the promising starting point towards a working electrically pumped light-emitting device.

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Section: Methodsmentioning

confidence: 77%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Intersubband Transition Engineering in the Conduction Band of Asymmetric Coupled Ge/SiGe Quantum Wells

et al. 2020

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“…The ACQW modules are separated by a 21-nm thick Si 0.2 Ge 0.8 spacer. The detailed structural characterization of the samples shows the high quality of the heterostructures and reproducibility of deposited thickness in the subnanometer range [25]. The samples investigated here were n-doped by P co-deposition in the wide Ge well.…”

Section: Introductionmentioning

confidence: 91%

“…Similar to the FTIR experiment, the samples were kept at cryogenic temperatures (TL = 6 K) in an optical He-flow cryostat. More experimental details can be found in References [22,25]. The TM-polarized electric field direction is indicated with a double-headed arrow.…”

Section: Introductionmentioning

confidence: 99%

Electron Population Dynamics in Optically Pumped Asymmetric Coupled Ge/SiGe Quantum Wells: Experiment and Models

et al. 2019

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n-type doped Ge quantum wells with SiGe barriers represent a promising heterostructure system for the development of radiation emitters in the terahertz range such as electrically pumped quantum cascade lasers and optically pumped quantum fountain lasers. The nonpolar lattice of Ge and SiGe provides electron–phonon scattering rates that are one order of magnitude lower than polar GaAs. We have developed a self-consistent numerical energy-balance model based on a rate equation approach which includes inelastic and elastic inter- and intra-subband scattering events and takes into account a realistic two-dimensional electron gas distribution in all the subband states of the Ge/SiGe quantum wells by considering subband-dependent electronic temperatures and chemical potentials. This full-subband model is compared here to the standard discrete-energy-level model, in which the material parameters are limited to few input values (scattering rates and radiative cross sections). To provide an experimental case study, we have epitaxially grown samples consisting of two asymmetric coupled quantum wells forming a three-level system, which we optically pump with a free electron laser. The benchmark quantity selected for model testing purposes is the saturation intensity at the 1→3 intersubband transition. The numerical quantum model prediction is in reasonable agreement with the experiments and therefore outperforms the discrete-energy-level analytical model, of which the prediction of the saturation intensity is off by a factor 3.

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Modulated Photoluminescence at Low Temperature Measurements with Controlled Electron Concentration in Asymmetric GaAs/GaAlAs/GaAs Quantum Wells

Belhassen

Karsenty

2022

Journal of Luminescence

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Control of Electron-State Coupling in Asymmetric Ge/Si−Ge Quantum Wells

Cited by 25 publications

References 34 publications

Intersubband Transition Engineering in the Conduction Band of Asymmetric Coupled Ge/SiGe Quantum Wells

Intersubband Transition Engineering in the Conduction Band of Asymmetric Coupled Ge/SiGe Quantum Wells

Electron Population Dynamics in Optically Pumped Asymmetric Coupled Ge/SiGe Quantum Wells: Experiment and Models

Modulated Photoluminescence at Low Temperature Measurements with Controlled Electron Concentration in Asymmetric GaAs/GaAlAs/GaAs Quantum Wells

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