Electron-hole liquid and excitonic molecules in quasi-two-dimensional SiGe layers of Si/SiGe/Si heterostructures

Burbaev, T. M.; Гордеев, М Н; Lobanov, D. N.; Новиков, А. В.; Rzaev, M. M.; Sibeldin, N. N.; Skorikov, M. L.; Tsvetkov, V. A.; Shepel, Denis

doi:10.1134/s002136401017008x

Cited by 20 publications

(8 citation statements)

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“…This is additionally facilitated by the electric field of nonequilibrium holes accumulating in the QW. As a result, spatially direct two-dimensional excitons and the EHL can form in the alloy layer [13][14][15][16][17][18]. It should be noted that, owing to the accumulation of excitons in the SiGe layer, the excitation-level threshold for the formation of the EHL at a given temperature is considerably lower for the QW than for the Si layers of the structure [12].…”

Section: Condensed Mattermentioning

confidence: 99%

“…Quite recently, an EHL was observed in the quantum wells (QWs) of type-I Si/SiO heterostructures [9][10][11] and type-II Si/SiGe heterostructures with a low Ge content [12][13][14][15][16][17]. 1 It was established that a quasi-two-dimensional EHL is formed in both type-I and type-II structures with sufficiently narrow QWs [10,11,[13][14][15][16][17]. In Si/SiGe structures, the formation of both spatially direct EHL and dipolar EHL with spatially separated electrons and holes is possible [17].…”

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confidence: 99%

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Heating and evaporation of a two-dimensional electron–hole liquid by heat pulses

et al. 2017

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The dynamics of low-temperature ( K) photoluminescence spectra of Si/Si Ge /Si heterostructures ( ) under the influence of a stream of nonequilibrium phonons (heat pulses) propagating in the structure is investigated. The rapid evaporation of the electron-hole liquid in the quantum well of the structure is observed as the liquid is heated by nonequilibrium phonons. It is established that an increase in the exciton-gas density in the quantum well is caused by the evaporation of the electron-hole liquid and by an increase in the rate of exciton capture by the quantum well. It is shown that the interaction with nonequilibrium phonons results in the dissociation of bound-exciton complexes in the Si layers, which is accompanied by an increase in the exciton concentration and lifetime.

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Section: Condensed Mattermentioning

confidence: 99%

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confidence: 99%

Heating and evaporation of a two-dimensional electron–hole liquid by heat pulses

et al. 2017

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“…Because the quantum efficiency (η) of the radiative process is determined by the relative magnitudes of the radiative recombination rate (k R ) and the non-radiative recombination rate (k NR ), a key to enhance η is increasing the k R and decreasing the k NR . To realize these requirements, several Si engineered materials have been studied where nanostructured Si systems such as nanocrystals [8][9][10], nanolayers [11][12][13], nanowires [14][15][16], and heterostructures with SiO 2 and Ge [17][18][19][20][21] have shown promising properties. However, there is still no faultless solution for achieving practical Si emitters.…”

Section: Introductionmentioning

confidence: 99%

Enhanced radiative recombination rate for electron-hole droplets in a silicon photonic crystal nanocavity

et al. 2017

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We investigate photoluminescence (PL) spectra and dynamics of clean silicon photonic crystal nanocavities at 10 K. A sharp emission peak due to the nanocavity mode has the largest intensity when the energy of the nanocavity mode is equal to the emission energy of the electron-hole droplets (EHD). Time-resolved PL spectroscopy indicates that the PL lifetime of the EHD is reduced to as short as 1.2 ns by the nanocavity mode. A careful analysis of the lifetimes indicates that the radiative recombination rate for EHD is enhanced with a factor of larger than 5 by the Purcell effect.

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“…In a number of semi conductors with an indirect fundamental absorption edge, in particular, in bulk Si [13] or SiGe/Si QWs [14], there are two mechanisms of the radiative recom bination of biexcitons that differ in the number of recombining electron-hole pairs. Conventional (1Eg) luminescence corresponds to the processes in which, upon the emission of a photon by a biexciton, there remains an electron-hole pair.…”

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confidence: 99%

Superradiance of a degenerate exciton gas in semiconductors with indirect fundamental absorption edge

et al. 2014

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In recent years, there has been a surge of interest in the phenomenon of superradiance, which can be observed upon the interaction of a phase locked (coherent) ensemble of emitters with an electromag netic field mode [1][2][3][4][5]. It is well known that one of the consequences of this interaction is the appearance of collective states in which the probability of sponta neous emission is proportional to the square of the number of emitting particles and, thus, is greatly enhanced [6]. To date, the occurrence of superradi ance has been reliably established only for atomic and quasi atomic systems, such as atoms in optical traps [1], quantum dots [7], and J aggregates [8]. At the same time, to the best of our knowledge, the possibility of the formation of superradiant states in a degenerate exciton gas in bulk semiconductors and semiconduc tor quantum wells (QWs) has not been investigated in detail despite considerable progress in attaining the regime of exciton Bose condensation [9,10]. Proba bly, this is related to the fact that the properties of a degenerate exciton gas in semiconductors with a direct fundamental absorption edge are described in terms of strong exciton-photon coupling, and the formalism developed by Dicke [6] cannot be applied. On the other hand, for semiconductors with an indirect absorption edge, the conservation of the quasimomen tum implies that the emission of a photon upon the recombination of an exciton requires either the partic ipation of a phonon or the presence of a short range potential. In this case, the observation of superradi ance is also impossible because the coherence is par tially lost in the final state (i.e., state in which the exci ton ensemble appears after the emission of a photon). Here, we demonstrate that, nevertheless, superradiant states in a system of excitons in an indirect gap semi conductor may be achievable with regard to 2Eg lumi nescence, i.e., the process in which two electron-hole pairs recombine simultaneously with the emission of one photon carrying away their net energy [11,12]. First, we give a qualitative theoretical description of the effect. Next, we present experimental results sup porting the possibility of the observation of superradi ance in SiGe/Si heterostructures.The possibility of the existence of superradiant states can be illustrated in the simplest way by the example of a degenerate gas of noninteracting (or weakly interacting) biexcitons. In a number of semi conductors with an indirect fundamental absorption edge, in particular, in bulk Si [13] or SiGe/Si QWs [14], there are two mechanisms of the radiative recom bination of biexcitons that differ in the number of recombining electron-hole pairs. Conventional (1Eg) luminescence corresponds to the processes in which, upon the emission of a photon by a biexciton, there remains an electron-hole pair. Weak emission with photon energy approximately twice as high as the band gap energy (2Eg luminescence) appears when, upon the simultaneous recombination of the two electronhole pairs comprising ...

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Electron-hole liquid and excitonic molecules in quasi-two-dimensional SiGe layers of Si/SiGe/Si heterostructures

Cited by 20 publications

References 10 publications

Heating and evaporation of a two-dimensional electron–hole liquid by heat pulses

Heating and evaporation of a two-dimensional electron–hole liquid by heat pulses

Enhanced radiative recombination rate for electron-hole droplets in a silicon photonic crystal nanocavity

Superradiance of a degenerate exciton gas in semiconductors with indirect fundamental absorption edge

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