Quantitative 3D mapping of carrier concentration in quantum-confined heterostructures for power and RF applications

Leuven - Master projects/internships
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More than two weeks ago

Explore microscopy on the nanometer scale

III-N is already recognized for bright and energy-saving white light sources, which eventually led to 2014 Nobel prize in physics to its inventors. With further advances in III-N semiconductors (GaN, AlN, InN) epitaxy in the past decade, GaN is turning out to be the first choice in power and electronic industry as well. This is because of the important technical advantages it has to offer, which includes 10× higher breakdown strength, faster switching speed, higher thermal conductivity and importantly, quasi defect-insensitive light emission properties. Its excellent current transport is accredited to quantum confinement of high-density carriers at its interface without the need of extrinsic doping. It is now, thus, confidently expanding over power-conversion applications including fast battery chargers, smartphones, computers, servers, automotive, lighting systems and photovoltaics, where it has tremendous potential to facilitate reduced power consumption. Emerging applications that are high-end solutions such as Light detection and ranging (LiDAR) applications, benefit significantly from the high commutations speed of GaN power devices. Wireless charging solutions based on GaN, highly anticipated to be adopted by industrial giants, is set to be a distinguished technology achievement.

In all scenarios, be it a smoother advancement of current III-N technology, novel device concepts or implementation of III-N nanostructures for devices, one of the main challenges is the quantitative characterization of doping and its spatial distribution over an extent from micron to nanoscale within multi-layer heterostructures with quantum confinement properties at the interfaces. Using routine characterization techniques, both doping concentration and its distribution cannot be assessed separately. For example, chemical concentration of the dopant assessed by secondary ion mass spectrometry or electron-beam based technique does not always reflect the actual active carrier concentration in these materials because of poor activation of p-type dopants and activation of dopants under irradiation. The thesis focuses on development of scanning spreading resistance microscopy (SSRM) on III-Ns. SSRM is known to be sensitive to free carrier concentration allowing its quantitative estimation at nanoscale and has already been implemented on Si, SiGe, III-Vs etc. It makes use of a sharp conducting probe to map two-dimensional spreading resistance, which can be converted into carrier concentration using a step-graded calibration sample. Therefore, the main objectives of the project are (1) understanding of current transport behavior at nanoscale, (2) improvement of back ohmic contacts for removing high series resistance and (3) study of phase transformation and defect generation at uniaxial pressures exceeding 30 GPa.

The student will be trained in advanced electrical SPM techniques Conductive Atomic Force Microscopy (C-AFM) and SSRM. In case of necessity for the deeper understanding of the results, complimentary material characterization analysis such as Transmission electron microscopy (TEM) and X-ray photoelectron microscopy (XPS) analysis can be availed. Knowledge of TCAD simulation or other numerical simulation is a plus. With the guidance of his supervisor, data interpretation and analysis will also be a major part of the thesis/internship. As such, the student will be guided in design of the experiment and understanding the resulting experimental data. A good command of English is required. Start data and project duration can be discussed.

Type of Project: Internship, thesis, combined internship/master thesis

Duration: 6 months

Master Program: Electrotechnics/Electrical Engineering, Physics, Nanoscience and Nanotechnology, Engineering

Supervising scientist: For more information on the project or for sending in your application contact Albert Minj (albert.minj@imec.be).
KU Leuven supervisor: Wilfried Vandervorst

Imec allowance will be provided

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