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Patel, D.; Interholzinger, K.; Thiagarajan, P.; Robinson, G. Y.; Menoni, C.S.

doi:10.1103/physrevb.53.12633

Cited by 8 publications

(8 citation statements)

References 13 publications

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“…Further increase of the photon energy dramatically increased a which reached values as large as 200 ps for photon energies around 2.02 eV. This behavior can be understood in relation to the conduction band structure of the In 0.48 Ga 0.52 P/ In 0.5 Al 0.5 P MQWs, 4,5 schematically shown in Fig. 2.…”

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confidence: 85%

“…In bulk unstrained In 0.48 Ga 0.52 P, L 1c is approximately 0.2 eV below X 1c and can be accessible from ⌫ 1c by injecting carriers with excess energies of ϳ0.1 eV, the ⌫ 1c -L 1c separation. 5 In MQWs even lower energies are sufficient as the separation of the MQW ground state (⌫ 1e ) and L 1c is further reduced with increased carrier confinement. In addition, real space carrier transfer to the indirect X 1c valleys in the barrier (X 1c b ) may also occur in the In 0.52 Ga 0.48 P/͑Al x Ga 1Ϫx ) 0.5 In 0.5 P MQWs when the barrier composition x is selected to be larger than 0.5 and the barrier becomes indirect.…”

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“…L 1c scattering is expected to become important in narrow lattice matched and in tensile strained InGaP/InAlP MQWs, in which the ⌫ 1e -L 1c separation is small. 5 Carrier transfer to X 1c b is also expected to modify the output characteristics of MQW lasers, when the separation of the lowest confined states and X 1c b is small, as it occurs in highly compressive and tensile InGaP/InAlP MQWs. 5 This work is supported by the National Science Foundation through Grant Nos.…”

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Effect of indirect Γ-L and Γ-X transfer on the carrier dynamics of InGaP/InAlP multiple quantum wells

Menoni

Buccafusca

Marconi

et al. 1997

Applied Physics Letters

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Indirect ⌫-L scattering within the well, and real space carrier transfer to the barrier X 1c states are shown to significantly affect the carrier dynamics in In 0.48 Ga 0.52 P/In 0.5 Al 0.5 P multiple quantum wells. When carriers transfer to the indirect states occurs, the carrier dynamics is modified by the slow return of the carriers from the low mobility states to the well. As a result, the absorption recovery time increases by almost an order of magnitude. Carrier transfer to the indirect states also increases the carrier lifetime to values characteristic of indirect recombination. © 1997 American Institute of Physics. ͓S0003-6951͑97͒03001-5͔In 0.48 Ga 0.52 P/͑Al x Ga 1Ϫx ) 0.5 In 0.5 P multiple quantum wells ͑MQWs͒ are commonly used in the design of visible semiconductor lasers operating around 650 nm. 1 In the last few years, an effort in the design of visible laser diodes has been directed towards obtaining devices operating at wavelengths as short as 630 nm.2 However, these devices have been found to have higher threshold current and higher temperature sensitivity than those operating at longer wavelength, characteristics which have been associated with poor electron confinement. 2Several factors can limit the electron confinement, such as a small conduction band discontinuity, or carrier transfer to indirect valleys. In the visible heterostructures the former can be essentially ruled out, as the conduction band discontinuity in the In 0.48 Ga 0.52 P/͑Al x Ga 1Ϫx ) 0.5 In 0.5 P system has been measured to be 70% of the direct band gap difference between the well and barrier materials for a wide range of Al compositions x. 3,4 Scattering to the indirect valleys on the other hand, can significantly affect the carrier confinement, providing a leakage channel for carriers to transfer to the high effective mass L 1c or X 1c valleys. In bulk unstrained In 0.48 Ga 0.52 P, L 1c is approximately 0.2 eV below X 1c and can be accessible from ⌫ 1c by injecting carriers with excess energies of ϳ0.1 eV, the ⌫ 1c -L 1c separation. 5 In MQWs even lower energies are sufficient as the separation of the MQW ground state (⌫ 1e ) and L 1c is further reduced with increased carrier confinement. In addition, real space carrier transfer to the indirect X 1c valleys in the barrier (X 1c b ) may also occur in the In 0.52 Ga 0.48 P/͑Al x Ga 1Ϫx ) 0.5 In 0.5 P MQWs when the barrier composition x is selected to be larger than 0.5 and the barrier becomes indirect. The associated decrease in the carrier mobility that accompanies this transfer has been shown to have dramatic effects on the threshold current of In 0.48 Ga 0.52 P/ (Al x Ga 1Ϫx ) 0.5 In 0.5 P lasers. 6 In this letter we present evidence of the important of ⌫-L scattering and real space ⌫-X carrier transfer on the carrier dynamics of In 0.48 Ga 0.5 P/In 0.5 Al 0.5 P MQWs and show that when carrier transfer to indirect states occurs, the carrier dynamics becomes dominated by the slow return of the carriers from the low mobility states to the well. As a result, the absorptio...

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Effect of indirect Γ-L and Γ-X transfer on the carrier dynamics of InGaP/InAlP multiple quantum wells

Menoni

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Marconi

et al. 1997

Applied Physics Letters

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“…Increased carrier confinement leads to (i) an electronic configuration in which multiple quantum wells (MQWs) of direct band-gap semiconductors become intrinsically indirect, i.e., L 1c or X 1c are the lowest conduction band states in the well, or (ii) a type II conduction band alignment with the lowest indirect conduction band state located in the barrier and the highest valence band state in the well. The former case is obtained in InGaP͞InAlP MQWs and the latter is observed in GaAs͞AlAs MQWs for well widths less than 35 Å [1,2].…”

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confidence: 88%

“…E͑P c ͒ is the energy at which the unperturbed states would cross; i.e., E G ͑P c ͒ E X ͑P c ͒ and V GX is the interaction or mixing potential. In our simulation, a G was elected to be the value of dE p ͞dp measured close to atmospheric pressure, and a X was set equal to 216 meV͞GPa, a typical value for the X pressure coefficient, and equal to that measured in InAs͞GaAs QDs [1,12,14]. Using a G , a X , and considering the X-excitonic band-gap energy to vary with dot size as E dot X 2.3 1 135.8992͞d 1.7165 [15], P c was calculated for each dot size within the ensemble.…”

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Three-Dimensional Confinement in the Conduction Band Structure of InP

et al. 2000

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Strong quantum confinement in InP is observed to significantly reduce the separation between the direct and indirect conduction band states. The effects of three-dimensional confinement are investigated by tailoring the initial separation between conduction band states using quantum dots (QDs) of different sizes and hydrostatic pressure. Analyses of the QD emission spectra show that the X 1c states are lowest in energy at pressures of ϳ6 GPa, much lower than in the bulk. The transition to the X 1c states can be explained by either a sequence of G-L and L-X crossings, or by the crossover between strongly coupled G and X states. PACS numbers: 71.24. + q, 71.55.Eq, 73.20.Dx, 78.55.Cr Quantum confinement has dramatic effects on the optical and electronic properties of semiconductors. Quantum confinement gives rise to electron states whose energy can be varied with the confinement dimensions, and dramatically changes the density of states from steplike in one-dimensionally confined quantum well systems to atomiclike in three-dimensionally confined quantum dots (QDs). The changes in the density of states and the possibility of tailoring the band gap have attracted attention for the application of quantum confined systems in the design of optoelectronic devices.In zinc blende quantum well structures, quantum confinement has also been found to alter the electronic structure. Increased carrier confinement leads to (i) an electronic configuration in which multiple quantum wells (MQWs) of direct band-gap semiconductors become intrinsically indirect, i.e., L 1c or X 1c are the lowest conduction band states in the well, or (ii) a type II conduction band alignment with the lowest indirect conduction band state located in the barrier and the highest valence band state in the well. The former case is obtained in InGaP͞InAlP MQWs and the latter is observed in GaAs͞AlAs MQWs for well widths less than 35 Å [1,2].In three-dimensionally confined systems, model calculations predict quantum confinement to significantly alter the electronic structure of zinc blende semiconductors as the lower effective mass G 1c state rises to higher energy much faster than the higher effective mass L 1c and X 1c states [3,4]. In strained III-V QDs grown epitaxially, the interplay between carrier confinement and strain could result in either a type II electronic configuration with X 1c -derived states in the capping layer and holes in G 1y -derived QD states, or in a type I configuration where the indirect states in the QD are lowest in energy [4]. Instead, in freestanding colloidal QDs, only an intrinsically indirect electronic configuration is possible [3,5]. The model calculations predict G-X transitions to be observed in freestanding GaAs QDs with diameter ,40 Å [6], and in InP QDs at pressures around 7 GPa, as confinement alone is not sufficient to lower the X-like states below G-like states even for zero dimension [3].In this Letter, we present the first experimental evidence showing that strong quantum confinement significantly reduces the se...

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