Epoxy bond and stop-etch (EBASE) technique enabling backside processing of (Al)GaAs heterostructures

Weckwerth, M.V.; Simmons, J. A.; Harff, N. E.; Sherwin, M.E.; Blount, M. A.; Baca, Wes Edmund; Chui, H. C.

doi:10.1006/spmi.1996.0115

Cited by 62 publications

(48 citation statements)

References 13 publications

(15 reference statements)

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“…To form the bottom electrode, the GaAs substrate was totally removed so that another NiCr electrode could be placed on the bottom in close proximity to the 2DHS (10000Å). Details of the substrate removal can be found elsewhere 12 . To measure the compressibility, we applied a 10 mV AC excitation voltage V ac to the bottom electrode (Gate 1), as shown in Fig.…”

Section: -10mentioning

confidence: 99%

Thermodynamic Signature of a Two-Dimensional Metal-Insulator Transition

2000

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We present a study of the compressibility, κ, of a two-dimensional hole system which exhibits a metal-insulator phase transition at zero magnetic field. It has been observed that dκ dp changes sign at the critical density for the metal-insulator transition. Measurements also indicate that the insulating phase is incompressible for all values of B. Finally, we show how the phase transition evolves as the magnetic field is varied and construct a phase diagram in the density-magnetic field plane for this system. 73.40.Hm, 71.30+h, 72.20.My Recently, we are seeing a growing body of experimental evidence supporting a metal-insulator quantum phase transition in a number of two-dimensional electron 1 and hole systems 2 where coulomb interactions are strong and particle mobility is quite high. These experiments are of interest because of the prevailing theory of noninteracting particle systems in two dimensions which states that only insulating behavior should be seen at all densities for even the smallest amount of disorder in the system.3 In order to further understand the nature of the unusual phase transition, it is important to study the thermodynamic properties near the transition. One particular question is whether there is any signature for the phase transition in a thermodynamic measurement. Theoretically, within the framework of Fermi liquid, one does not expect any qualitative change in the thermodynamic properties.4 On the other hand, recent theories for strong interacting systems 5,6 have predicted that there should be profound consequences in thermodynamic measurements.In this paper, we address this issue by presenting a measurement of one of the fundamental thermodynamic quantities: the thermodynamic density of states (or equivalently, the compressibility) of a strongly interacting two-dimensional hole system (2DHS). We report evidence that the compressibility measurement indeed provides an unambiguous signature for the metalinsulator transition (MIT). The insulating phase is incompressible. Furthermore, we show that the phase transition at B = 0 is intimately related to the quantum Hall state to insulator transition for the lowest Landau level in a finite magnetic field.Traditionally, to obtain the density of states (DOS) or the compressibility of a 2D electron system, capacitance between the 2D electrons and the gate is measured. 7-10This capacitance can be modeled as the geometrical capacitance in series with a quantum capacitance. The quantum capacitance per unit area c q is related to the DOS dn dµ by c q = e 2 dn dµ , or to κ by c q = n 2 e 2 κ where µ is the chemical potential and n is the carrier density. One major drawback of this method is that, in the low magnetic field limit, the quantum capacitance is much larger than the geometric capacitance. For two capacitors in series, small uncertainty in the geometric capacitance can lead to a large quantitative error (even a sign error) in the extracted κ. In a pioneering experiment by Eisenstein et al.11 , the penetration of the electric field thr...

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Section: -10mentioning

confidence: 99%

Thermodynamic Signature of a Two-Dimensional Metal-Insulator Transition

2000

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“…Using our previously developed epoxy-bond-and-stop-etch (EBASE) technique [9] a pair of vertically aligned split gates is defined by electron beam lithography on each side of a double quantum well heterostructure whose thickness is only 0.8 pn. This use of close-proximity split gates on both sides of the epitaxial layers allows the width of each quantum wire to be independently controlled.…”

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confidence: 99%

Magnetoresistance of one-dimensional subbands in tunnel-coupled double quantum wires

et al. 1999

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We study the low-temperature in-plane magnetoresistance of tunnel-coupled quasi-onedimensional quantum wires. The wires are defined by two pairs of mutually aligned split gates on opposite sides of a I 1 micron thick AlGaAsIGaAs double quantum well heterostructure, allowing independent control of their widths. In the ballistic regime, when both wires are defined and the field is perpendicular to the current, a large resistance peak at -6 Tesla is observed with a strong gate voltage dependence. The data is consistent with a counting model whereby the number of subbands crossing the Fermi level chan, Des with fie!d due to the formation of an anticrossing in each pair of ID subbands.

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“…In addition, (2) the energy of the transition can be readily controlled by a gate voltage and/or source drain bias VSD, which makes it possible to obtain a tunable THz detector. A more detailed discussion about the device operation and fabrication can be found in [16]- [21].…”

Section: Principle Of Operationmentioning

confidence: 99%

“…Then, the EBASE technique [21] is used to finish the fabricate of the DQW structure by adding front and back gates. Here, we briefly discuss the basic steps involved in the device fabrication as shown in Figure 3, and a more detailed discussion about the fabrication process is found in [21]. Tile first step is to grow the double quantum well epitaxial structure on a sacrificial substrate.…”

Section: Photon Photonmentioning

confidence: 99%

A Bowtie Antenna Coupled Tunable Photon-Assisted Tunneling Double Quantum Well (DQW) THz Detector

2001

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The integration of a bowtie antenna with a double electron layer tunneling transistor (DELTT) device for the purposes of THz detection is investigated in this paper. The concept of THz detection, based on photon-assisted tunneling (PAT) between the two electron layers in a double quantum well (DQW) heterostructure, will be explained. The detector is expected to have narrowband, electrically tunable, fast response, and the possibility to operate at relatively high temperatures. Since the active area of the detector is very small, which is necessary to achieve fast response, it is not efficient in collecting THz radiation. Therefore, a broadband bowtie antenna is integrated with the detector to efficiently collect the THz radiation. Characteristics of different bowtie antenna geometries at THz frequencies were studied. An equivalent circuit model of the THz detector was developed, for the first time, to estimate the impedance characteristics at THz frequencies. Such a model is crucial for achieving impedance matching between the DELTT and the antenna to increase the overall coupling efficiency.

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Epoxy bond and stop-etch (EBASE) technique enabling backside processing of (Al)GaAs heterostructures

Cited by 62 publications

References 13 publications

Thermodynamic Signature of a Two-Dimensional Metal-Insulator Transition

Thermodynamic Signature of a Two-Dimensional Metal-Insulator Transition

Magnetoresistance of one-dimensional subbands in tunnel-coupled double quantum wires

A Bowtie Antenna Coupled Tunable Photon-Assisted Tunneling Double Quantum Well (DQW) THz Detector

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