Ultra-low resistive ohmic contacts on n-GaN using Si implantation

Burm, Jinwook; Chu, K.; Davis, William A.; Schaff, William J.; Eastman, L.F.; Eustis, T. J.

doi:10.1063/1.118182

Cited by 110 publications

(37 citation statements)

References 10 publications

(9 reference statements)

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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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“…For these reasons, post-implantation anneals used in the fabrication of GaN-based electronics have been performed at growth temperatures ͑ϳ1100°C͒ as in the GaN junction field-effect transistor reported by Zolper et al 3 and the ultralow contact resistance achieved by Burm et al on Si-implanted GaN ͑0.097 ⍀ mm͒. 4 Recently, we have observed threading dislocation motion, reaction, and resultant reduction by adopting a rapid annealing technique at 1500°C with 100 bar N 2 overpressure. A removable AlN capping layer was used to protect the GaN during the anneal, and smooth pit-free surfaces were observed after annealing.…”

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confidence: 99%

Effect of nitridation on polarity, microstructure, and morphology of AlN films

Hanlon

Kaeding

et al. 2004

Applied Physics Letters

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The polarity of AlN epitaxial layers grown on (0001) sapphire, SiC, and nitrided sapphire substrates was examined by convergent beam electron diffraction, and the morphology and microstructure were characterized by atomic force microscopy and scattering contrast transmission electron microscopy (TEM). The AlN films grown on sapphire and SiC without a buffer layer or nitridation of the substrate were flat and had Al polarity. From TEM studies in both cross section and plan view, it was found that the threading dislocation (TD) density was ∼1×108 and 2×1010 cm−2 for screw-component and pure edge component dislocations, respectively. N-face AlN was realized by pregrowth nitridation of sapphire substrates, but these films contained a small volume fraction of Al-face inversion domains which were related to hexagonal pyramids defined by {11̄02} facets. The density of screw-component TDs was significantly reduced due to nitridation. Cross-sectional TEM showed that the film grown on nitrided sapphire was almost free of screw-component TDs and that the density of pure edge TDs was ∼4×109 cm−2.

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“…The first approach was to use Si implantation into the HFETs to increase the electron concentration to facilitate carrier tunneling across the contact [4][5][6][7][8] . We picked sample #4 (the worst case) in Table 2 as a test vehicle to examine the implantation approach; we assumed that if the contact behavior on sample #4 could be improved, then all other samples could be improved using the same approach.…”

Section: Approaches To Fabricate Low Resistance-contact In a Morementioning

confidence: 99%

Contact Issues of GaN Technology

Qiao

Lau

et al. 1999

MRS Internet j. nitride semicond. res.

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In this paper, we discuss the issue of fabricating reliable and reproducible ohmic contacts on AlGaN HFET structures. During the course of our investigation of fabricating contacts to HFETs, we found that the contact properties could vary significantly from one sample to another, even though they were nominally the same. This problem was prominently manifested in the ohmic contact behavior. The origin of this problem was traced back to the variation of the HFET structure during growth. In this paper, we report an attempt to fabricate reproducible ohmic contacts of these structures.

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Ultra-low resistive ohmic contacts on n-GaN using Si implantation

Cited by 110 publications

References 10 publications

Cryogenic Control Architecture for Large-Scale Quantum Computing

Cryogenic Control Architecture for Large-Scale Quantum Computing

Effect of nitridation on polarity, microstructure, and morphology of AlN films

Contact Issues of GaN Technology

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