Observation of Tunable Band Gap and Two-Dimensional Subbands in a Novel GaAs Superlattice

Döhler, G. H.; Künzel, H.; Olego, D. J.; Ploog, K.; Ruden, P.P.; Stolz, H.; Abstreiter, G.

doi:10.1103/physrevlett.47.864

Cited by 175 publications

(24 citation statements)

References 9 publications

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“…Due to the larger effective mass of heavy holes and the resulting larger acceptor binding energy, holes will populate an acceptor band rather than valence subbands. 6 And the number of subbands for holes, the two-dimensional state density of holes are much larger than that of electrons. Therefore it is difficult to populate holes in high index valence subbands or the con- The American Physical Society tinuum valence band both by photoexcitation and thermal excitation when compared with that for electrons.…”

Section: -11mentioning

confidence: 99%

Temperature dependence of photoluminescence of ann-i-p-iGaAs superlattice

Wang

et al. 2000

Phys. Rev. B

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Both the photoluminescence peaks corresponding to the vertical transitions and the nonvertical transitions in an n-i-p-i GaAs superlattice are clearly observed. The redshifts of the two peaks with increasing temperature are discussed in terms of the temperature-dependent carrier separation effect.Since the concept of doping superlattice was proposed by Esak and Tsu, 1 the electronic properties of it were intensively investigated both theoretically and experimentally. 2-11Doping superlattices are structures which contain alternatively n-type and p-type doped regions of one semiconductor material and have a number of unique properties, such as tunable electronic structures, indirect band gap in real space, and large recombination lifetimes. These properties are originated from the spatial separation of electrons and holes due to the periodic impurity space charge potential and can be utilized in semiconductor devices such as light-intensity modulators. Great efforts have been put on the tunable and indirect band-gap transitions of n-i-p-i superlattices. The possible vertical optical transitions in n-i-p-i superlattices are also investigated by temperature-dependent photoluminescence ͑PL͒ experiments.7-9 However, these reports only discussed the overall PL intensity dependence on temperature and the critical temperature point at which vertical transitions will prevail in intensity according to the sample parameters. To our surprise, no discussions on the PL peak energy dependence on temperature were performed in the large body of previous research in this field. In this paper, we investigate the temperature-dependent PL properties of an n-i-p-i

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Section: -11mentioning

confidence: 99%

Temperature dependence of photoluminescence of ann-i-p-iGaAs superlattice

Wang

et al. 2000

Phys. Rev. B

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“…2 Some of the unusual properties of these so-called "nipi crystals" such as a tunable band gap and two-dimensional subbands have recently been reported for nipi structures based on GaAs. 3 It is but a small step to imagine superlattices based on amorphous hydrogenated silicon (<2-Si:H), a material that is known to be dopable. 4 Such a superlattice combines aspects of a crystalline periodic structure in the direction perpendicular to the layers with the amorphous nature of the material that it is based on.…”

Section: R Cariusmentioning

confidence: 99%

Carrier Recombination Times in Amorphous-Silicon Doping Superlattices

1984

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Doping superlattices, i.e., multilayer structures consisting of ultrathin (50 A ^ d =^ 400 A) tf-type, intrinsic, and /Mype layers of a-S'r.W (nipi structures), have been produced. Up to a tenfold increase in their infrared photoconductivity after band-gap illumination compared to unstructured a-Si:H is observed. The results are well described by a simple model for the carrier recombination kinetics that takes into account the spatial separation of electrons and holes due to the modulation of the band energies.

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“…These changes of PL spectra with the increase of excitation intensity finally saturate because the photogenerated electron-hole separation reduces, and finally cancels, the built-in electric field. Now we compare our PL results of the n-i-p-i sample with similar works, [3][4][5][6][7][8] where many-body effects ͑or charging effects͒ in QD's were investigated. In these studies, the QD's were filled with electrons by doping.…”

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confidence: 94%

Photoluminescence of InAs quantum dots inn-i-p-iGaAs superlattice

Wang

Chen

et al. 2000

Phys. Rev. B

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Large blueshift and linewidth increase in photoluminescence ͑PL͒ spectra of InAs quantum dots ͑QD's͒ in n-i-p-i GaAs superlattice were observed. By increasing the excitation intensity from 0.5 to 32 W/cm 2 , the PL peak position blueshifted 18 meV, and the linewidth increased by 20 meV. Such large changes are due to the state-filling effects of the QD's resulted from the separation of photogenerated electrons and holes caused by the doping potential.The optical properties of InAs self-assembled quantum dots ͑QD's͒ have been of great interest in recent years. The interband and intraband optical transitions of these QD's are widely studied, both for the interest in fundamental physical properties and for the development of QD lasers and photodetectors. It is important to investigate electron-hole separation effects in QD's and design QD structures that can separate and store photoexcited carriers for memory-device applications. However, few works were done in this field. Recently, Schoenfeld et al.1 have designed a QD device that can separate and store photoexcited electrons and holes. Their structure consisted of two GaAs quantum wells of different thickness, separated by a thin AlAs barrier. An InAs QD layer is inserted in the thick quantum well. The strain these InAs QD's create induces QD's within the thin GaAs quantum well that are coupled to the InAs QD's in the thick well. In their structure, photogenerated electrons and holes are spatially separated into the InAs QD's and strain-induced QD's, respectively.In this work, we study a different QD structure designed to spatially separate and store photogenerated electrons and holes. In this structure, InAs self-assembled QD's were grown in the n-type and p-type regions of a n-i-p-i GaAs superlattice. Photogenerated electrons and holes in GaAs barriers are expected to be swept by the intrinsic electric field to the n-doped regions and the p-doped regions, respectively, and trapped by the InAs QD's there. As the photogenerated electrons and holes fill up the lower QD states, photoluminescence ͑PL͒ properties of these InAs QD's different from conventional QD's inserted in intrinsic GaAs layers are expected. In our PL experiments, large blueshift of the PL peak and increase of the PL linewidth with increasing excitation intensity were observed for the QD's in the n-i-p-i GaAs superlattice, whereas for similar InAs QD's in intrinsic GaAs layers, only a small blueshift of the PL peak and increase of the linewidth were observed. The large blueshift in the n-ip-i QD's is a clear indication of the state filling of the QD's due to electron-hole separation.The samples were grown by molecular-beam epitaxy on a ͑001͒ N ϩ GaAs substrate. After deposition of a 1-m semiinsulating GaAs type buffer layer, 10 periods of n-type GaAs ͑20 nm͒/InAs QD's (2 ML)/n-type GaAs (20 nm)/p-type GaAs ͑20 nm͒/InAs QD's (2 ML)/p-type GaAs ͑20 nm͒ were grown. The n-type regions were Si doped and the p-type regions were Be doped; both n and p doping concentrations are 1ϫ10 18 cm Ϫ3 . The growth t...

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Observation of Tunable Band Gap and Two-Dimensional Subbands in a Novel GaAs Superlattice

Cited by 175 publications

References 9 publications

Temperature dependence of photoluminescence of ann-i-p-iGaAs superlattice

Temperature dependence of photoluminescence of ann-i-p-iGaAs superlattice

Carrier Recombination Times in Amorphous-Silicon Doping Superlattices

Photoluminescence of InAs quantum dots inn-i-p-iGaAs superlattice

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