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Chand, Naresh; Henderson, T.; Klem, John F.; Masselink, W. T.; Fischer, R.; Chang, Yia‐Chung; Morkoç, H.

doi:10.1103/physrevb.30.4481

Cited by 410 publications

(68 citation statements)

References 29 publications

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“…Upon cooling the sample from room temperature, the quantum well is populated with electrons from the deepest hydrogenic donor state, and some electrons remain bound on the donor atoms which act as DX centers. Upon illumination, the DX-bound electrons are excited to higher energy metastable states 14,15,25,26 , which they can leave only via thermal excitation. At temperatures from 15-25 K electrons are then excited from the metastable state and fall either into the QW or into shallow hydrogenic impurity levels in the donor layer.…”

mentioning

confidence: 99%

Donor binding energy and thermally activated persistent photoconductivity in high mobility (001) AlAs quantum wells

Dasgupta

Knaak

Moser

et al. 2007

Applied Physics Letters

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A doping series of AlAs (001) quantum wells with Si δ-modulation doping on both sides reveals different dark and post-illumination saturation densities, as well as temperature dependent photoconductivity. The lower dark two-dimensional electron density saturation is explained assuming deep binding energy of ∆DK = 65.2 meV for Si-donors in the dark. Persistent photoconductivity (PPC) is observed upon illumination, with higher saturation density indicating shallow post-illumination donor binding energy. The photoconductivity is thermally activated, with 4 K illumination requiring post-illumination annealing to T = 30 K to saturate the PPC. Dark and post-illumination doping efficiencies are reported.PACS numbers: 73.20.b,73.21.fg,73.50.Pz,73.43.f,71.18.+y Two dimensional electron systems (2DESs) in aluminum arsenide (AlAs) quantum wells (QWs) are interesting for their valley degeneracy and heavy mass 1,2,3 . The valley index quantum number acts as an extra pseudospin degree of freedom, and the heavy mass allows interactions to play a larger role at a given density 4 . Recently progress has also been made in fabricating and characterizing one-dimensional AlAs nanostructures 5,6,7 . Although improvements in high mobility AlAs 2DES structures have been reported 8,9 , many important material parameters such as the donor binding energy and doping efficiency have been obscured by substrate charge effects 10 . Since these parameters are instrumental in designing and optimizing heterostructures, we have performed a systematic study on double-sided-doped quantum wells which screen away unwelcome substrate effects. In the process, we also identify a thermally activated persistent photoconductivity (PPC) not previously reported.AlAs is an indirect band gap III-V semiconductor with three degenerate conduction band valleys at the X-points of the Brillouin zone edge. In (001) growth, the biaxial strain between AlAs and Al x Ga 1−x As (x = 0.45) decreases the energy of the two in-plane valleys such that for wide wells W > 55Å, 11,12 only these two valleys are degenerately occupied. In AlAs, the longitudinal and transverse electron masses are anisotropic, m l = 1.1 m e and m t = 0.2 m e , respectively 3 , and the effective Landé g-factor g * = 2 (Ref. 11).Free electrons in AlAs/AlGaAs heterostructures come from two different sources: intentional Si-dopant and un-

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confidence: 99%

Donor binding energy and thermally activated persistent photoconductivity in high mobility (001) AlAs quantum wells

Dasgupta

Knaak

Moser

et al. 2007

Applied Physics Letters

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“…The barriers are obtained using Al x Ga 1−x As with x = 0.33. With this Al concentration, the conduction band discontinuity at the Γ point is ∆E c 295 meV and the AlGaAs is a direct gap semiconductor with the X minima about 60 meV above the Γ valley (i.e., 355 = (∆E c + 60) meV above that of GaAs) [14]. The active region design is based on a "anticrossed diagonal" scheme, where the wavefunction of the excited state of the laser transition (n = 3) has a reduced overlap with the lower state (n = 2) [15].…”

Section: Design and Operation Of A Gaas/algaas Quantum Cascade Lasersmentioning

confidence: 99%

GaAs Quantum Cascade Lasers: Fundamentals and Performance

Sirtori

2002

Les Lasers : Applications Aux Technologies De l'Information Et Au Traitement Des Matériaux

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Abstract. Quantum engineering of the electronic energy levels and tailoring of the wavefunctions in GaAs/Al x Ga 1−x As heterostructures allows to obtain the correct matrix elements and scattering rates which enable laser action between subbands. This article reviews the state-of-the-art of GaAs based quantum cascade lasers. These new light sources operate, with peak power in excess of 1 W at 77 K, in the 8-13 µm wavelength region, greatly extending the wavelength range of GaAs optoelectronic technology. Waveguides are based on an Al-free design with an appropriate doping profile which allows optical confinement, low losses and optimal heat dissipation. Finally, new active region designs aiming to improve the laser temperature dependence are discussed. Recent results on these devices confirm that the ratio between the conduction band discontinuity and the photon energy (∆E c /E laser ) is the dominant parameter controlling their thermal characteristic. The maximum operating temperature of these devices is 280 K for lasers with emission wavelength at ∼11 µm.

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“…In Al x Ga 1-x As, the impurities of Si are shallow donors, as it was reported in the ref. [25] . Moreover, at sufficient electron heating by the applied electric fields (see Section 4), the major part of electrons can transfer from the donor states to the conduction band.…”

Section: Electrostatics Of the Barrier Layermentioning

confidence: 99%

Untitled

2015

Semicond. Phys. Quantum Electron. Optoelectron.

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Abstract. Steady-state electric characteristics of quantum heterostructures Al x Ga 1-x As/GaAs/Al x Ga 1-x As with  -doped barriers have been analyzed in this work. It has been shown that at high doping the additional low-conductive channels are formed in the barrier layers. Current-voltage characteristics of the structure were obtained in the wide interval of applied electric fields up to several kV/cm being based on the solution of Boltzmann transport equation. It has been found that in the electric fields higher than 1 kV/cm the effect of exchange of the carriers between the high-conductive channel of the GaAs quantum well and the channels in the AlGaAs barriers becomes essential. This effect gives rise to the appearance of the strongly nonlinear current-voltage characteristics with a portion of negative differential conductivity. The developed model of heterostructure is adequate to those recently fabricated and studied by Prof. Sarbey's group. The obtained results explain some observation of this paper. It has been found that the effect of electron real-space transfer takes place at both low temperatures and room temperatures, which opens perspectives to design novel type nanostructured current controlled devices.

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Comprehensive analysis of Si-dopedAlxGa1−xAs(
Naresh Chand
¹
,
T. Henderson
²
,
John F. Klem
³

et al.

Cited by 410 publications

References 29 publications

Donor binding energy and thermally activated persistent photoconductivity in high mobility (001) AlAs quantum wells

Donor binding energy and thermally activated persistent photoconductivity in high mobility (001) AlAs quantum wells

GaAs Quantum Cascade Lasers: Fundamentals and Performance

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Comprehensive analysis of Si-dopedAlxGa1−xAs(Naresh Chand1, T. Henderson2, John F. Klem3 et al.

Cited by 410 publications

References 29 publications

Donor binding energy and thermally activated persistent photoconductivity in high mobility (001) AlAs quantum wells

Donor binding energy and thermally activated persistent photoconductivity in high mobility (001) AlAs quantum wells

GaAs Quantum Cascade Lasers: Fundamentals and Performance

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Comprehensive analysis of Si-dopedAlxGa1−xAs(
Naresh Chand
¹
,
T. Henderson
²
,
John F. Klem
³

et al.