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Offers : 66

READ OUT architecture FOR Large scale silicon quantum computing

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Start date : 1 October 2020

offer n° SL-DRT-20-1270

Quantum computers may soon be able to solve problems beyond the reach of conventional computers. Such computers no longer manipulate electrons as particles, but as waves that maintain phase relationships and can interfere. The preparation, coherent manipulation and reading of quantum states is extremely challenging. One promising option for making quantum bits (qubits) is to store electrons in silicon quantum dots and manipulate their spin. The CEA Grenoble fabricates and characterizes such devices, and develops appropriate tools for their modeling. The objective of the PhD is to design and electrically characterize a read-out architecture for large scale quantum computing. The student is expected to work on innovative integration scheme to overcome the challenges of initialization and readout in large arrays of quantum dots. The architecture will have to comply with quantum error correction protocols implementation and will need to take into account the material specificities of silicon spin qubits.

The PhD thesis will rely on a preliminary simulation study on the impact of the layout of these arrays, of their dimensions, and of the choice of materials on the physics of the qubits.

  • Keywords : Engineering sciences, Technological challenges, Electronics and microelectronics - Optoelectronics, Emerging materials and processes for nanotechnologies and microelectronics, DCOS, Leti
  • Laboratory : DCOS / Leti
  • CEA code : SL-DRT-20-1270
  • Contact : maud.vinet@cea.fr

Reliability of power amplifiers: modeling, design and test strategies

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Start date : 1 October 2020

offer n° SL-DRT-20-1251

With the rise of 5G, RF and millimeter circuits are increasing in the telecommunications sector. In the reception / transmission chain, the power amplifier (PA) is a key element and it is critical to the proper functioning of transmissions. The reliability of the latter is an important element because the RF excursions at the terminals of the device are strong and the signal shapes are complex, bringing dynamic aging mechanisms into play. In this context, the designer must rely on aging simulation tools to be able to correctly size his circuit.

One of the first objectives of the thesis is to better understand the aging mechanisms put into play at the CMOS level through stress campaigns in DC and in broad signal RF on a Load-Pull bench. The transistors studied will be MOS with fine oxide as well as devices optimized for high power (DMOS). Then, different topologies of the power stage will be studied in order to correlate the design with a possible gain in reliability. Finally, an in-situ monitoring system for the degradation of the device will be proposed to compensate for performance losses or to alert in the event of an imminent failure.

  • Keywords : Engineering sciences, Electronics and microelectronics - Optoelectronics, DCOS, Leti
  • Laboratory : DCOS / Leti
  • CEA code : SL-DRT-20-1251
  • Contact : alexis.divay@cea.fr

Study of dynamic degradation and reliability of advanced GaN on Si power devices

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Start date : 1 October 2020

offer n° SL-DRT-20-0430

GaN-on-Si based power devices are now considered as the next generation of mass market devices for high frequency & low looses power converters (DC/DC, AC/DC or DC/AC). In this vision, LETI is developing its own pîlot line of GaN on Si power devices (CMOS compatible) from the GaN epitaxy to the final power module. These devices are supposed to operate dynamically between high voltage stage (650V and below) and high current state (> 20A) at high frequencies (> 100kHz). Statics and dynamic performances being proved, it is worth of interest to test and study reliability of these devices under high voltage stress and high temperature as well as under practical swithching conditions (hard/soft/ZVS). These studies aim to understand the underlying physical degradation mechanisms arising under operating conditions and ultimately to stabilize the technologie for industrial technological transfer.

The PhD student will be responsible of :

– Finalizing exisiting dynamic setups and create new ones especially concerning on-wafer switching test (limitations/feasibility)

– In Depth study of HEMT electrical parameters degradation (Ron, Vt, Sw…) as well as Diode parameters (Vf, Sw) during DC or AC stress to determine the root cause of the degradation leading to reliability reduction.

– Determination of Switching SOA of GaN based devices from LETI as well as studying new acceleration factors such as duty factor or switching frequency

– Localization and Identification of Failure point and understanding of the Failure root cause through FA studies (IR or visible camera + FIB/MEB studies)

– Proposal of new technological solutions to overcome some early failures and low realiblity issues

The PhD student will be curious, open minded and team worker.

  • Keywords : Engineering sciences, Technological challenges, Electronics and microelectronics - Optoelectronics, Emerging materials and processes for nanotechnologies and microelectronics, DCOS, Leti
  • Laboratory : DCOS / Leti
  • CEA code : SL-DRT-20-0430
  • Contact : william.vandendaele@cea.fr

Resonators and devices based on elastic waves obtained through the hybridization of surface and bulk waves

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Start date : 1 September 2020

offer n° SL-DRT-20-0668

Bulk or surface elastic wave devices are currently an enabling technology for radiofrequency emission/reception circuits used in mobile phones. Since, at constant frequency, the wavelength of elastic wave is close to 100,000 times smaller than electromagnetic wavelengths, the treatment of a signal carried by elastic waves instead of an electrical signal offers a tremendous miniaturization. With the increase in frequency bands operated simultaneously by each single mobile phone, requirements brought onto radiofrequency filters become more and more stringent. This motivates the research on new types of components exploiting new elastic waves. Conventional technologies rely on bulk acoustic waves (BAW) or surface acoustic waves (SAW) propagating respectively along the thickness or the surface of a piezoelectric material. Such kind of materials offer the possibility to couple electric signals into elastic waves, and conversely. In the last few years, a new kind of propagation mode, called “hybrid SAW/BAW” has been proposed, based on the excitation of waves by a periodic array of piezoelectric stubs. First realizations have been proposed, but their properties are not yet fully determined.

This PhD subject focuses therefore on the study of the potentialities offered by these new kinds of modes. On one hand, the properties of such waves are strongly related to the combination of piezolectric material, of the nature of the substrate, on their respective crystal orientations as well as on the geometric dimensions of the piezoelectric stubs. The candidate will therefore investigate the design space in order to reveal what performances can be expected from such structures and optimise their design towards applications such as RF filters or time references, ideally for applications above 3 GHz. This work will leverage the simulation models available at CEA-LETI and those developped by the FrecNSys company.

A second part of the PhD is expected also to explore more fundamental possibilites opened by these modes arising from the coupling between elastic surface waves and a periodic array of electrically active structures. Such periodic structures belong to the broader range of so-called elastic metamaterials, which offer unusual propagation properties such as frequency ranges in which wave propagation is forbidden, artificial slowing of waves, strong confinement or nonreciprocal propagation. Since active structures are involved, additional interesting effects may be explored. The candidate will leverage the expertise on elastic metamaterials brought by the acoustic department of ISEN.

Eventually, an experimental part will be devoted to the proposition of designs to be implemented in the clean rooms of CEA-LETI and participation to the technological developments. The goal is here to assess the exprimental feasibility of such structures.

  • Keywords : Engineering sciences, Technological challenges, Communication networks, IOT, radiofrequencies and antennas, Electronics and microelectronics - Optoelectronics, DCOS, Leti
  • Laboratory : DCOS / Leti
  • CEA code : SL-DRT-20-0668
  • Contact : alexandre.reinhardt@cea.fr

Piezoelectric MEMS actuator hydraulically amplified

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Start date : 1 September 2020

offer n° SL-DRT-20-0488

The main objective of micro-actuators research is an architecture that can generate large displacements and forces over a wide frequency range, while not consuming a significant amount of electrical power. To date, no solution meets all these criteria. Indeed hydraulic actuators do not meet the criterion of compactness and frequency but allow significant force and displacement. Similarly, electromagnetic actuators have a good frequency range with excellent force and stroke output, but they are generally heavy and require significant electrical current. Piezoelectrics are also known for their excellent operating bandwidth and can generate large forces in a compact size, but traditionally they have very small displacements.

The technological breakthrough of the thesis will consist to develop a hydraulic amplification mechanism, by applying small displacements on a large surface, sa as to move a liquid, and to generate, by conservation of the volume, important displacements on a weaker moving surface.

Therefore, the thesis will consist to develop and integrate into a MEMS (Micro Electro-Mechanical System) system, this hydraulically amplified piezoelectric actuator (called HDAM system for “Hydraulic Displacement Amplification Mechanism”) and optimize it

  • Keywords : Engineering sciences, Technological challenges, Cyber physical systems - sensors and actuators, Electronics and microelectronics - Optoelectronics, DCOS, Leti
  • Laboratory : DCOS / Leti
  • CEA code : SL-DRT-20-0488
  • Contact : laurent.mollard@cea.fr
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