Control of electric field domain formation in multiquantum well structures

Shakouri, Ali; Grave, I.; Xu, Yunjian; Ghaffari, A.; Yariv, Amnon

doi:10.1063/1.109793

Cited by 21 publications

(5 citation statements)

References 12 publications

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“…In a multistack GaAs/(Al,Ga)As quantum well infrared detector, special switching properties were observed, which were attributed to the formation and readjustment of HFDs in the structure [296]. Subsequently, Shakouri et al [297] discussed the important parameters which govern the formation, expansion and readjustment of EFDs in multi-quantum-well structures. The pattern of EFD formation can be manipulated by a careful design of the device.…”

Section: Detectorsmentioning

confidence: 99%

Non-linear dynamics of semiconductor superlattices

2005

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In the last decade, non-linear dynamical transport in semiconductor superlattices (SLs) has witnessed significant progress in theoretical descriptions as well as in experimentally observed non-linear phenomena. However, until now, a clear distinction between non-linear transport in strongly and weakly coupled SLs was missing, although it is necessary to provide a detailed description of the observed phenomena. In this review, strongly coupled SLs are described by spatially continuous equations and display self-sustained current oscillations due to the periodic motion of a charge dipole as in the Gunn effect for bulk semiconductors. In contrast, weakly coupled SLs have to be described by spatially discrete equations. Therefore, weakly coupled SLs exhibit a more complex dynamical behaviour than strongly coupled ones, which includes the formation of stationary electric field domains, pinning or propagation of domain walls consisting of a charge monopole, switching between stationary domains, self-sustained current oscillations due to the recycling motion of a charge monopole and chaos. This review summarizes the existing theories and the experimentally observed non-linear phenomena for both types of semiconductor SLs.

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Section: Detectorsmentioning

confidence: 99%

Non-linear dynamics of semiconductor superlattices

2005

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“…This is due to moving to high field transport regime and possible formation of nonuniform electric field domains in the device which is beyond the scope of this article. 47 For another verification of our model, we calculated and plotted the current-voltage curves for the photodetectors ͑200 m diameter͒ of Ref. 43.…”

Section: Appendix: Comparison With Experimental Datamentioning

confidence: 99%

Electronic and thermoelectric transport in semiconductor and metallic superlattices

Vashaee

Shakouri

2004

Journal of Applied Physics

142

124

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A detailed theory of nonisothermal electron transport perpendicular to multilayer superlattice structures is presented. The current-voltage (I-V) characteristics and the cooling power density are calculated using Fermi-Dirac statistics, density-of-states for a finite quantum well and the quantum mechanical reflection coefficient. The resulting equations are valid in a wide range of temperatures and electric fields. It is shown that conservation of lateral momentum plays an important role in the device characteristics. If the lateral momentum of the hot electrons is conserved in the thermionic emission process, only carriers with sufficiently large kinetic energy perpendicular to the barrier can pass over it and cool the emitter junction. However, if there is no conservation of lateral momentum, the number of electrons participating in a thermionic emission will increase. This has a significant effect on the I-V measurements as well as the cooling characteristics. Theoretical calculations are compared with the experimental dark current characteristics of quantum well infrared photodetectors and good agreement over a wide temperature range for a variety of superlattice structures is obtained. In contrast with earlier studies, it is shown that lateral momentum is conserved for the case of electron transport in planar semiconductor barriers.

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“…It has been observed before that the conservation of lateral momentum in the tunneling process between wells induces current peaks whenever energy levels of adjacent wells are aligned. [8][9][10][11] This leads to an instability which causes formation of high and low field domains ͑HFD, LFD͒ in the device. In the HFD, there is ground level-to-excited level sequential resonant tunneling ͑SRT͒.…”

Section: Form Approved Omb No 0704-0188mentioning

confidence: 99%

Quantum interference effect and electric field domain formation in quantum well infrared photodetectors

Shakouri

Yariv

1995

Applied Physics Letters

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An observation of quantum interference effect in photocurrent spectra of a weakly coupled bound-to-continuum multiple quantum well photodetector is reported. This effect persists even at high biases where the Kronig-Penney minibands of periodic superlattice potential in the continuum are destroyed. Our results show that electrons remain coherent over a distance of 40-50 nm. The observation was used to investigate electric field domain formation induced by sequential resonant tunneling in the superlattice. A large off-resonant energy level alignment between two neighboring wells in the high field domain was observed. © 1995 American Institute of Physics.Recently, there has been great interest in studying optical and transport properties of multiple quantum well ͑MQW͒ structures. In these ''artificial molecules,'' energy quantization and wave nature of carriers have been used to design new devices and to demonstrate some basic laws of quantum mechanics, e.g., to observe minibands in the continuum of periodic potential superlattice, 1 to observe suppression of optical absorption in coupled potential wells, 2 and to make quantum well infrared photodetectors ͑QWIPs͒ by using minibands in the continuum.3 In this letter, we report on a new observation of a quantum interference effect in the photocurrent spectra in bound-to-continuum QWIPs. Using this effect, we analyze the electric field domain formation in the superlattice.In a weakly coupled MQW structure with two bound states in each well ͑i.e., a bound-to-bound QWIP͒, 3 the absorption spectrum is a Lorentzian shape peak corresponding to a transition between the ground state and the first excited state. The contribution of other states in the continuum above the barrier is negligible because of the oscillator strength sum rule ͑one-to-two transition, both states being localized in the well, has a much more significant transition dipole matrix element͒.When the quantum well parameters allow only one state in the well ͑i.e., a bound-to-continuum QWIP͒, the absorption spectrum is not Lorentzian any more, the states above the barriers have a strong contribution to the absorption. Because these continuum states are extended over the barriers and several neighboring wells ͑depending on the coherence length of electrons͒, electron interference effects can be observed in the absorption spectrum. At zero bias, due to the potential translation symmetry there are well-known minibands in the continuum states of the superlattice 1 which can be calculated using, for example, the Kronig-Penney model. The miniband energy gaps, depending on the overlap of the states between neighboring wells, can be designed large enough to be observable in the absorption spectrum. However, under an applied bias, such that the voltage drop per period is bigger than these energy gaps, the miniband structure is destroyed. We will show that in a QWIP even at large biases, one can still see some features in the photocurrent spectrum which are due to electron interference effects over one or two periods ...

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Control of electric field domain formation in multiquantum well structures

Cited by 21 publications

References 12 publications

Non-linear dynamics of semiconductor superlattices

Non-linear dynamics of semiconductor superlattices

Electronic and thermoelectric transport in semiconductor and metallic superlattices

Quantum interference effect and electric field domain formation in quantum well infrared photodetectors

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