Thermal breakdown, bistability, and complex high-frequency current oscillations due to carrier heating in superlattices

Steuer, Haiko; Wacker, A.; Schöll, Eckehard; Ellmauer, Michael; Schomburg, E.; Renk, K. F.

doi:10.1063/1.126254

Cited by 11 publications

(9 citation statements)

References 10 publications

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“…Recently, an additional S-type current-voltage characteristics has been found in strongly coupled superlattices due to electron heating [208]. The combination of N-type and S-type negative differential conductivity may provide additional interesting effcets.…”

Section: Discussionmentioning

confidence: 99%

Semiconductor superlattices: a model system for nonlinear transport

2002

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Electric transport in semiconductor superlattices is dominated by pronounced negative differential conductivity. In this report the standard transport theories for superlattices, i.e. miniband conduction, Wannier-Stark-hopping, and sequential tunneling, are reviewed in detail. Their relation to each other is clarified by a comparison with a quantum transport model based on nonequilibrium Green functions. It is demonstrated how the occurrence of negative differential conductivity causes inhomogeneous electric field distributions, yielding either a characteristic sawtooth shape of the current-voltage characteristic or self-sustained current oscillations. An additional ac-voltage in the THz range is included in the theory as well. The results display absolute negative conductance, photon-assisted tunneling, the possibility of gain, and a negative tunneling capacitance. 2 Notation and list of symbolsThroughout this work we consider a superlattice, which is grown in the z direction. Vectors within the (x, y) plane parallel to the interfaces are denoted by bold face letters k, r, while vectors in 3 dimensional space are r, k, . . . . All sums and integrals extend from −∞ to ∞ if not stated otherwise.The following relations are frequently used in this work and are given here for easy reference:

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Section: Discussionmentioning

confidence: 99%

Semiconductor superlattices: a model system for nonlinear transport

2002

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“…In order to develop high-power SL oscillators for submillimetre radiation, the impact of electron heating and of the mesa size on the I -V characteristics was investigated theoretically [285,286] and experimentally [286,287] for strongly coupled SLs. The relatively large miniband width in strongly coupled SLs causes an additional heating instability, which appears as an S-shaped I -V characteristic in addition to the conventional N-type one occurring at lower electric fields [285].…”

Section: Gigahertz Oscillatorsmentioning

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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“…This ignores hot-carrier effects and it is not correct in general. Somewhat more general models with an average electron temperature T i at the ith SL period have been proposed, including a phenomenological equation for the temperature [77]. A general derivation of the balance equations (including the equation for the temperature) would clarify these issues.…”

Section: Assumptions and The Discrete Drift-diffusion Modelmentioning

confidence: 99%

“…(3) Discrete hydrodynamics. Recently it has been argued that experimentally observed self-oscillations in certain strongly coupled SL can be explained by using a discrete model having different electron temperatures in different SL periods [77]. It would be interesting to derive discrete hydrodynamic equations for electron density, momentum, and temperature plus electric potential from a quantum kinetic formulation.…”

Section: Final Remarksmentioning

confidence: 99%

Theory of nonlinear charge transport, wave propagation, and self-oscillations in semiconductor superlattices

Bonilla¹

2002

J. Phys.: Condens. Matter

141

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Nonlinear charge transport in semiconductor superlattices under strong electric fields parallel to the growth direction results in rich dynamical behaviour including the formation of electric field domains, pinning or propagation of domain walls, self-sustained oscillations of the current and chaos. Theories of these effects use reduced descriptions of transport in terms of average charge densities, electric fields, etc. This is simpler when the main transport mechanism is resonant tunnelling of electrons between adjacent wells followed by fast scattering between subbands. In this case, we will derive microscopically appropriate discrete models and boundary conditions. Their analyses reveal differences between low-field behaviour where domain walls may move oppositely or parallel to electrons, and high-field behaviour where they can only follow the electron flow. The dynamics is controlled by the amount of charge available in the superlattice and doping at the injecting contact. When the charge inside the wells becomes large, boundaries between electric field domains are pinned resulting in multistable stationary solutions. Lower charge inside the wells results in self-sustained oscillations of the current due to recycling and motion of domain walls, which are formed by charge monopoles (high contact doping) or dipoles (low contact doping). Besides explaining wave motion and subsequent current oscillations, we will show how the latter depend on such controlling parameters as voltage, doping, temperature, and photoexcitation.

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Thermal breakdown, bistability, and complex high-frequency current oscillations due to carrier heating in superlattices

Cited by 11 publications

References 10 publications

Semiconductor superlattices: a model system for nonlinear transport

Semiconductor superlattices: a model system for nonlinear transport

Non-linear dynamics of semiconductor superlattices

Theory of nonlinear charge transport, wave propagation, and self-oscillations in semiconductor superlattices

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