Ohmic contacts to III–V compound semiconductors: A review of fabrication techniques

Piotrowska, A.; Guivarc’h, A.; Pelous, G.

doi:10.1016/0038-1101(83)90083-7

Cited by 179 publications

(29 citation statements)

References 117 publications

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“…For these prototype devices a large insertion loss of 10-20 dB is observed, owing mostly to the resistance of the ohmic contacts, which deviates from 50 Ω. Precise control of the contact resistance and capacitance using ion- implantation can overcome this limitation and also dramatically shrink the footprint of these devices 24,25 . The time-domain response of the switch is demonstrated by amplitude modulating an applied 120 MHz constant wave tone, as shown in Fig.…”

Section: A Hemt Switching Elementsmentioning

confidence: 99%

Cryogenic Control Architecture for Large-Scale Quantum Computing

et al. 2015

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Solid-state qubits have recently advanced to the level that enables them, in principle, to be scaledup into fault-tolerant quantum computers. As these physical qubits continue to advance, meeting the challenge of realising a quantum machine will also require the engineering of new classical hardware and control architectures with complexity far beyond the systems used in today's fewqubit experiments. Here, we report a micro-architecture for controlling and reading out qubits during the execution of a quantum algorithm such as an error correcting code. We demonstrate the basic principles of this architecture in a configuration that distributes components of the control system across different temperature stages of a dilution refrigerator, as determined by the available cooling power. The combined setup includes a cryogenic field-programmable gate array (FPGA) controlling a switching matrix at 20 millikelvin which, in turn, manipulates a semiconductor qubit.Realising the classical control system of a quantum computer is a formidable scientific and engineering challenge in its own right 1,2 . The hardware that comprises the control interface must be fast relative to the timescales of qubit decoherence, low-noise so as not to further disturb the fragile operation of qubits, and scalable with respect to physical resources, ensuring that the footprint for routing signal lines or the operating power does not grow rapidly as the number of qubits increases 3,4 . As solid-state quantum processors will likely operate below 1 kelvin 5-8 , components of the control system will also need to function in a cryogenic environment, adding further constraints.Similar challenges have long been addressed in the satellite and space exploration community 9 , where the need for high-frequency electronic systems operating reliably in extreme environments has driven the development of new circuits and devices 10 . Quantum computing systems, on the other hand, have to date largely relied on brute-force approaches, controlling a few qubits directly via room temperature electronics that is hardwired to the quantum device at cryogenic temperatures.Here we present a control architecture for operating a cryogenic quantum processor autonomously and demonstrate its basic building blocks using a semiconductor qubit. This architecture addresses many aspects related to scalability of the control interface by embedding multiplexing sub-systems at cryogenic temperatures and separating the high-bandwidth analog control waveforms from the digital addressing needed to select qubits for manipulation. Our demonstration comprises a commercial field-programmable gate array (FPGA) operating at 4 kelvin and controlling a microwave signal switching matrix at 20 mK, which then interfaces with a quantum dot device. Bringing these sub-systems together in the context of our control architecture suggests a path for scaleup of control hardware needed to manipulate the large numbers of qubits in a useful quantum machine. I. CONTROL MICRO-ARCHITECTUREOur control micro-...

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Section: A Hemt Switching Elementsmentioning

confidence: 99%

Cryogenic Control Architecture for Large-Scale Quantum Computing

et al. 2015

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“…In addition to a wide variety of device and circuit applications, good quality ohmic contacts are required for investigating the physical and electrical properties of bulk materials and related III-V heterostructures. Consequently, much attention has been recently devoted to the development of ohmic contacts to III-V materials, and the research area include both, the fundamental behavior of metal/semiconductor contacts and the new techniques for improving the properties of ohmic contacts [1][2][3][4][5][6][7].…”

Section: Criteria For a Good Ohmic Contactmentioning

confidence: 99%

Ohmic Contacts to GaAs: Fundamentals and Practice

Piotrowska

1993

Acta Phys. Pol. A

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Recent advances in the technology and understanding of ohmic contacts to GaAs are presented. The paper emphasizes the reactions at the metal/GaAs interface and the structural factors which govern its electrical behavior and long-term stability. Results on the optimization of conventional gold-based ohmic contacts together with recent achievements in the technology of non-alloyed.contacts are overviewed.PACS numbers: 73.40Ns Criteria for a good ohmic contactModern device concepts strongly depend on reliable and well-controlled electrical contacts through which one has to communicate with the interior of the device from the outside world. In particular, micron and submicron size Ill-V devices can be fully exploited only with adequate ohmic contacts. In addition to a wide variety of device and circuit applications, good quality ohmic contacts are required for investigating the physical and electrical properties of bulk materials and related III-V heterostructures. Consequently, much attention has been recently devoted to the development of ohmic contacts to III-V materials, and the research area include both, the fundamental behavior of metal/semiconductor contacts and the new techniques for improving the properties of ohmic contacts [1][2][3][4][5][6][7].The purpose of this paper is to bring together much of the fundamental and practical knowledge on the formation of ohmic contacts to GaAs. First, we give brief overview of the requirements for ohmic contacts in modern GaAs devices. Next, we shall comment on the actual state of understanding of the formation of potential barriers developing at metal/GaAs interfaces. While the detailed discussion of theories of metal/GaAs interface is beyond the scope of this article, basic concepts applicable to fabricate low-resistance contacts will be provided. The main part of the paper is devoted to up-todate approaches in the fabrication of ohmic contacts. We shall emphasize the reactions at the metal/semiconductor interface and the stuctural factors which govern its electrical behavior and long-term stability. Key technological issues of advanced contact technology will be given in Sec. 4.The main constraint on the choice of material for an ohmic contact is to ensure that it has the correct electrical properties. They are characterized by the (491)

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“…Besides, Au-Ge or Au-Ge-Ni alloys have also been extensively used in ohmic contacts to GaAs semiconductors [13,14]. Knowledge of the Au-Ge-Ni ternary system is also very important for their application in the semiconductor industry.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation and thermodynamic modeling of the Au–Ge–Ni system

et al. 2012

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Phase equilibria in the Au-Ge-Ni ternary system were studied by means of scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and differential scanning calorimetry. The phase relations in the solid state at 600°C as well as a vertical section at Au 72 Ge 28 -Ni were established. No ternary compound was found at 600°C. On the basis of the experimental phase equilibria data, a thermodynamic model of the Au-Ge-Ni ternary system was developed using the CALPHAD method. Thermodynamically calculated phase diagrams are shown at 600°C, in two vertical sections and the liquidus projection. Reasonable agreement between the calculations and the experimental results was achieved.

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Ohmic contacts to III–V compound semiconductors: A review of fabrication techniques

Cited by 179 publications

References 117 publications

Cryogenic Control Architecture for Large-Scale Quantum Computing

Cryogenic Control Architecture for Large-Scale Quantum Computing

Ohmic Contacts to GaAs: Fundamentals and Practice

Experimental investigation and thermodynamic modeling of the Au–Ge–Ni system

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