Electronic States and Optical Transitions in Semiconductor Heterostructures

Vasko, F. T.; Kuznetsov, Alex V.

doi:10.1007/978-1-4612-0535-7

Cited by 127 publications

(163 citation statements)

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“…Following Ref. [19], we assume that the conduction band offset between a GL and WS 2 barrier and the effective electron mass in WS 2 are equal to 0.4 eV and 0.27 of the free electron mass, respectively [29]. Figure 4 shows the dependence of the matrix element |z u,l | 2 on the energy difference between the Dirac points ∆ and the value of the depolarization shift (dependent of |z u,l | 2 ) for different thicknesses of the WS 2 inter-GL barrier.…”

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confidence: 99%

Injection terahertz laser using the resonant inter-layer radiative transitions in double-graphene-layer structure

Ryzhii

Dubinov

Aleshkin

et al. 2013

Applied Physics Letters

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We propose and substantiate the concept of terahertz (THz) laser enabled by the resonant electron radiative transitions between graphene layers (GLs) in double-GL structures. We estimate the THz gain for TM-mode exhibiting very low Drude absorption in GLs and show that the gain can exceed the losses in metal-metal waveguides at the low end of the THz range. The spectrum of the emitted photons can be tuned by the applied voltage. A weak temperature dependence of the THz gain promotes an effective operation at room temperature.The gapless energy spectrum of graphene layers (GLs) [1] enables the creation of different terahertz (THz) devices utilizing the interband transition. In particular, the interband population inversion and the pertinent negativity of the dynamic conductivity in GLs [2,3] due to the optical or injection pumping can be used in GL-based THz lasers [4][5][6][7][8][9]. First experimental results on the THz emission from optically excited GLs [10] (see also review paper [11] and references therein) instill confidence in the realization of such lasers. One of the obstacles, limiting the achievement of the negative dynamic conductivity in the range of a few THz, is the reabsorption of the photons with the in-plane polarization emitted at the interband transitions due to the intraband transitions (the Drude absorption). Similar situation takes place in the quantum cascade lasers (QCLs) based on multiple quantum well (MQW) structures [12]. However, in the case of the photon polarization perpendicular to the QW plane the intraband (intrasubband) absorption can be much weaker than that following from the semi-classical Drude formula [13].In this paper, we propose a device structure based on a double-GL structure shown in Fig. 1 (upper panel) with the injection of electrons to one n-doped GL and to another p-doped GL, which can be used for lasing of THz photons with the electric field perpendicular to the GL plane due to the tunneling inter-GL radiative processes. The structure band diagram under the applied bias voltage and tunneling transitions assisted with the emission of photons with the energy ω ∼ ∆, where ∆ is the energy distance (gap) between the Dirac points in GLs, are demonstrated in Fig. 1 (lower panel). These transitions take place from the conduction band of the GL with 2DEG to the empty conduction band of GL with 2DHG. The transition from the filled valence band the former GL to the empty portion of the valence band of the latter GL also contribute to the emission of photons with ω ∼ ∆. The structure comprises two GLs with the side contact at one of the GL edges. This double-GL structure plays the role of the laser active region. The opposite edge of GL is isolated from another contact. A narrow tunneling-transparent barrier separates GLs (its thickness d is about few nanometers). The applied bias voltage V provides the formation of the two-dimensional electron and hole gases (2DEG and 2DHG) in the upper and lower GLs, respectively owing to the injection from the side contacts, so that the ...

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confidence: 99%

Injection terahertz laser using the resonant inter-layer radiative transitions in double-graphene-layer structure

Ryzhii

Dubinov

Aleshkin

et al. 2013

Applied Physics Letters

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“…The expression for absorption coefficient due to light-induced inter-band transitions is a measure of the strength of the optical matrix element. 36,37 Inter-band optical absorption from a populated valence band eigen state to an empty conduction band state requires the determination of the optical inter-band transition matrix elements |P + cv | 2 and |P − cv | 2 for right and left circularly-polarized light,respectively. P x cv , for instance, for right circularly polarized light is nominally defined as…”

Section: Circular Dichroism In Strained Graphenementioning

confidence: 99%

The tuning of light-matter coupling and dichroism in graphene for enhanced absorption: Implications for graphene-based optical absorption devices

Rakheja

Sengupta

2016

J. Phys. D: Appl. Phys.

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The inter-band optical absorption in graphene characterized by its fine-structure constant has a universal value of 2.3% independent of the material parameters. However, for several graphenebased photonic applications, enhanced optical absorption in graphene is highly desired. In this work, we quantify the tunability of optical absorption in graphene via the Fermi level in graphene, angle of incidence of the incident polarized light, and the dielectric constant of the surrounding dielectric media in which graphene is embedded. The influence of impurities adsorbed on the surface of graphene on the Lorentzian broadening of the spectral function of the density of states is analytically evaluated within the equilibrium Green's function formalism. Finally, we compute the differential absorption of right and left circularly-polarized light in graphene that is uniaxially and optically strained. The preferential absorption or circular dichroism is investigated for armchair and zigzag strain.

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“…Actually, χ takes into account the spin-orbit coupling due to the abrupt potential of the heterojunction at each interface, as [3,11] …”

Section: Eigenstate Problemmentioning

confidence: 99%

“…Peculiarities of ρ(ε) can be analyzed experimentally through the photoluminescence excitation (PLE) intensity for the case of near-edge absorption, I P LE , because both quantities are related by [11] …”

Section: Eigenstate Problemmentioning

confidence: 99%

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Abrupt barrier contribution to electron spin splitting in asymmetric coupled double quantum wells

Hernández‐Cabrera

Aceituno

2014

Indian J Phys

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We have studied the behavior of the electronic energy spin-splitting of InGaAs − InAlAs based double quantum wells (narrow gap structures) under in-plane magnetic and transverse electric fields. We have developed an improved 8 × 8 version of the Transfer Matrix Approach that consider contributions from abrupt interfaces and external fields when tunneling through central barrier exists. We have included the Landé g-factor dependence on the external applied field. Also, we have calculated electron density of states and photoluminescence excitation. Variations of the electron spin-splitting energy lead to marked peculiarities in the density of states.Because the density of states is directly related to photoluminescence excitation, these peculiarities are observable by this technique.

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Electronic States and Optical Transitions in Semiconductor Heterostructures

Cited by 127 publications

References 0 publications

Injection terahertz laser using the resonant inter-layer radiative transitions in double-graphene-layer structure

Injection terahertz laser using the resonant inter-layer radiative transitions in double-graphene-layer structure

The tuning of light-matter coupling and dichroism in graphene for enhanced absorption: Implications for graphene-based optical absorption devices

Abrupt barrier contribution to electron spin splitting in asymmetric coupled double quantum wells

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