N-type ohmic contacts to undoped GaAs/AlGaAs quantum wells using only front-sided processing: application to ambipolar FETs

Taneja, Deepyanti; Sfigakis, F.; Croxall, A. F.; Gupta, K. Das; Narayan, Vijay; Waldie, J.; Farrer, I.; Ritchie, D. A.

doi:10.1088/0268-1242/31/6/065013

Cited by 11 publications

(9 citation statements)

References 44 publications

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“…However the r i disorder corresponding to the resultant temperatures T is probably close to the actually frozen one. It should also be noted that the simulated freezing temperatures of localized charges are almost two times higher than the actual temperatures of post-growth dielectric and gate deposition operations [5][6][7][8][9][10][11][12].…”

Section: Comparison: Calculation Vs Experimentsmentioning

confidence: 92%

“…In contrast to the standard modulation doping method, the 2D gas is in this case is created at low temperatures by bias V g between the metallic gate and metallic contacts connected to the GaAs working layer [5][6][7][8][9][10][11]. The charge on the surface of the GaAs protective layer is generated in equilibrium at V g = 0 and a high temperature, along with the image charge in the metal, and a common Fermi level is established in the metal / dielectric / undoped semiconductor structure (Fig.…”

Section: Test Object and Suggested Modelmentioning

confidence: 99%

“…Little is known however about this phenomenon in undoped GaAs/AlGaAs structures. A study of these structures containing gate-induced 2D quantum electron or hole systems has been initiated recently [5][6][7][8][9][10][11][12]. The situation with a thin gate dielectric and shallow location of gate-induced systems is of interest for studying the role of surface charges [11,12] and for the development of quantum systems with ultimately small characteristic lateral sizes [13].…”

Section: Introductionmentioning

confidence: 99%

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Effect of surface charge self-organization on gate-induced 2D electron and hole systems

Ткаченко¹,

Ткаченко²,

Baksheev³

et al. 2020

MoEM

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A simple model has been suggested for describing self-organization of localized charges and quantum scattering in undoped GaAs/AlGaAs structures with 2D electron or hole gas created by applying respective gate bias. It has been assumed that these metal / dielectric / undoped semiconductor structures exhibit predominant carrier scattering at localized surface charges which can be located at any point of the plane imitating the GaAs / dielectric interface. The suggested model considers all these surface charges and respective image charges in metallic gate as a closed thermostated system. Electrostatic self-organization in this system has been studied numerically for thermodynamic equilibrium states using the Metropolis algorithm over a wide temperature range. We show that at T > 100 K a simple formula derived from the theory of single-component 2D plasma yields virtually the same behavior of structural factor at small wave numbers as the one given by the Metropolis algorithm. The scattering times of gate-induced carriers are described with formulas in which the structural factor characterizes frozen disorder in the system. The main contribution in these formulas is due to behavior of the structural factor at small wave numbers. Calculation using these formulas for the case of disorder corresponding to infinite T has yielded 2–3 times lower scattering times than experimentally obtained ones. We have found that the theory agrees with experiment at disorder freezing temperatures T ≈ 1000 K for 2D electron gas specimen and T ≈ 700 K for 2D hole gas specimen. These figures are the upper estimates of freezing temperature for test structures since the model ignores all the disorder factors except temperature.

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Section: Comparison: Calculation Vs Experimentsmentioning

confidence: 92%

Section: Test Object and Suggested Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of surface charge self-organization on gate-induced 2D electron and hole systems

Ткаченко¹,

Ткаченко²,

Baksheev³

et al. 2020

MoEM

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“…The AuGe/Ni/Au material was first used by [9] to make an ohmic contact to n-GaAs in 1967. Subsequent studies aimed at improving such contacts and understanding the annealing mechanisms [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Later on, with the increasing importance of the 2DEG in a GaAs/Al x Ga 1−x As heterostructure, research focussed on making ohmic contacts to the buried 2DEG [25][26][27][28][29][30][31][32][33].…”

Section: Introductionmentioning

confidence: 99%

Characterization of low-resistance ohmic contacts to a two-dimensional electron gas in a GaAs/AlGaAs heterostructure

Iqbal

Reuter

Wieck

et al. 2020

Eur. Phys. J. Appl. Phys.

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The study of electron transport in low-dimensional systems is of importance, not only from a fundamental point of view, but also for future electronic and spintronic devices. In this context heterostructures containing a two-dimensional electron gas (2DEG) are a key technology. In particular GaAs/AlGaAs heterostructures, with a 2DEG at typically 100 nm below the surface, are widely studied. In order to explore electron transport in such systems, low-resistance ohmic contacts are required that connect the 2DEG to macroscopic measurement leads at the surface. Here we report on designing and measuring a dedicated device for unraveling the various resistance contributions in such contacts, which include pristine 2DEG series resistance, the 2DEG resistance under a contact, the contact resistance itself, and the influence of pressing a bonding wire onto a contact. We also report here a recipe for contacts with very low resistance values that remain below 10 Ω for annealing times between 20 and 350 s, hence providing the flexibility to use this method for materials with different 2DEG depths. The type of heating, temperature ramp rate and gas forming used for annealing is found to strongly influence the annealing process and hence the quality of the resulting contacts. *

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“…and length µ = L m 1120 , Ohmic contacts were fabricated as described in [7], and finally top-gate electrodes were deposited to induce and tune the carrier concentration. All measurements reported here were conducted in a He-3 cryostat with a base temperature of 0.3 K with magnetic fields of up to 10 T. Four-terminal constant current measurements were performed using standard low frequency (≈12 Hz) AC lock-in techniques.…”

mentioning

confidence: 99%

Reappearance of linear hole transport in an ambipolar undoped GaAs/AlGaAs quantum well

Taneja

Shlimak

Narayan

et al. 2017

J. Phys.: Condens. Matter

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Ambipolar transport, or the ability to switch between electrons and holes in the same device, has strong implications towards the implementation of functional devices: for instance, creating gate-defined n-and p-type conducting channels in the same device can be exploited in thermoelectric power generation, as well as towards spintronic applications by tuning between large (holes) and small (electrons) spinorbit coupling. Equally, ambipolar transport is also of much interest in fundamental studies of scattering, interaction and spin related phenomena since electrons and holes have very different effective masses, band structures and spin properties [1,2]. Chen et al [1] and Croxall et al [2] studied the density dependence of µ p and µ e in ambipolar GaAs/AlGaAs single heterojunction devices and quantum wells (QWs) respectively. The mobilities were found to depend not only on the AbstractWe report the results of an investigation of ambipolar transport in a quantum well of 15 nm width in an undoped GaAs/AlGaAs structure, which was populated either by electrons or holes using positive or negative gate voltage V tg , respectively. More attention was focussed on the low concentration of electrons n and holes p near the metal-insulator transition (MIT). It is shown that the electron mobility µ e increases almost linearly with increase of n and is independent of temperature T in the interval 0.3 K-1.4 K, while the hole mobility µ p depends non-monotonically on p and T. This difference is explained on the basis of the different effective masses of electrons and holes in GaAs. Intriguingly, we observe that at low p the source-drain current (I SD )-voltage (V) characteristics, which become non-linear beyond a certain I SD , exhibit a re-entrant linear regime at even higher I SD . We find, remarkably, that the departure and reappearance of linear behaviour are not due to non-linear response of the system, but due to an intrinsic mechanism by which there is a reduction in the net number of mobile carriers. This effect is interpreted as evidence of inhomogeneity of the conductive 2D layer in the vicinity of MIT and trapping of holes in 'dead ends' of insulating islands. Our results provide insights into transport mechanisms as well as the spatial structure of the 2D conducting medium near the 2D MIT.Keywords: non-linear I-V characteristics, two-dimensional hole gas, metal-insulator transition (Some figures may appear in colour only in the online journal)Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.1361-648X/17/185302+7$33.00

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N-type ohmic contacts to undoped GaAs/AlGaAs quantum wells using only front-sided processing: application to ambipolar FETs

Cited by 11 publications

References 44 publications

Effect of surface charge self-organization on gate-induced 2D electron and hole systems

Effect of surface charge self-organization on gate-induced 2D electron and hole systems

Characterization of low-resistance ohmic contacts to a two-dimensional electron gas in a GaAs/AlGaAs heterostructure

Reappearance of linear hole transport in an ambipolar undoped GaAs/AlGaAs quantum well

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