Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Artificially introduced atomic-level sensors enable measurements of the electric field within a working semiconductor device

02.02.2017

Semiconductors lie at the heart of many of the electronic devices that govern our daily lives. The proper functioning of semiconductor devices relies on their internally generated electric fields. Being able to measure these fields on the nanoscale is crucial for the development of next-generation electronics, but present techniques have been restricted to measurements of the electric field at a semiconductor's surface.

A group of Takayuki Iwasaki, Mutsuko Hatano and colleagues at the Tokyo Institute of Technology, the Japan Science and Technology Agency (JST) and Toshiharu Makino at the National Institute of Advanced Industrial Science and Technology (AIST) has reported a new method for sensing internal electric fields at the interior of operating semiconductor devices.


Left: Schematic of the structure of the NV center. Middle: Confocal fluorescence image of a single NV center in the device. Right: Schematic of the measurement configuration.

Credit: Tokyo Institute of Technology

The technique exploits the response of an artificially introduced single electron spin to variations in its surrounding electric field, and enabled the researchers to study a semiconductor diode subject to bias voltages of up to 150 V.

Iwasaki and co-workers applied their method to diamond, a so-called wide-band-gap semiconductor in which the electric fields can become very strong -- a property important for low-loss electronic applications. Diamond has the advantage that it easily accommodates nitrogen-vacancy (NV) centers, a type of point defect that arises when two neighboring carbon atoms are removed from the diamond lattice and one of them is replaced by a nitrogen atom.

NV centers can be routinely created in diamond by means of ion implantation. A nearby electric field affects an NV center's energy state, which in turn can be probed by a method called optically detected magnetic resonance (ODMR).

The researchers first fabricated a diamond p-i-n diode (an intrinsic diamond layer sandwiched between an electron- and a hole-doped layer) embedded with NV centers. They then localized an NV center in the bulk of the i-layer, several hundreds of nanometers away from the interface, and recorded its ODMR spectrum for increasing bias voltages. From these spectra, values for the electric field could be obtained using theoretical formulas. The experimental values were then compared with numerical results obtained with a device simulator and found to be in good agreement -- confirming the potential of NV centers as local electric-field sensors.

Iwasaki and colleagues explain that the experimentally determined value for the electric field around a given NV center is essentially the field's component perpendicular to the direction of the NV center -- aligned along one of four possible directions in the diamond lattice. They reason that a regular matrix of implanted NV centers should enable reconstructing the electric field with a spatial resolution of about 10 nm by combining with super-resolution techniques, which is promising for studying more complex devices in further studies.

The researchers also point out that electric-field sensing is not only relevant for electronic devices, but also for electrochemical applications: the efficiency of electrochemical reactions taking place between a semiconductor and a solution depends on the former's internal electric field. In addition, Iwasaki and co-workers note that their approach need not be restricted to NV centers in diamond: similar single-electron-spin structures exist in other semiconductors like e.g. silicon carbide.

Background

Wide-band-gap semiconductors

Semiconducting materials feature a so-called band gap: an energy range wherein no accessible energy levels exist. In order for a semiconductor to conduct, electrons must acquire sufficient energy to overcome the band gap; controlling electronic transitions across the band gap forms the basis of semiconducting device action. Typical semiconductors like silicon or gallium arsenide have a band gap of the order of 1 electron volt (eV). Wide-band-gap semiconductors, like diamond or silicon carbide, have a larger band gap -- values as high as 3-5 eV are not uncommon.

Due to their large band gap, wide-band-gap semiconductors can operate at temperatures over 300 °C. In addition, they can sustain high voltages and currents. Because of these properties, wide-band-gap semiconductors have many applications, including light-emitting diodes, transducers, alternative-energy devices and high-power components. For further development of these and other future applications, it is essential to be able to characterize wide-band-gap devices in operation. The technique proposed by Iwasaki and colleagues for measuring the electric field generated in a wide-band-gap semiconductor subject to large bias voltages is therefore a crucial step forward.

Nitrogen-vacancy centers

Diamond consists of carbon atoms arranged on a lattice where each atom has four neighbors forming a tetrahedron. The diamond lattice is prone to defects; one such defect is the nitrogen-vacancy (NV) center, which can be thought of as resulting from replacing a carbon atom with a nitrogen atom and removing one neighboring carbon atom. The energy level of an NV center lies in the band gap of diamond but is sensitive to its local environment. In particular, the so-called nuclear hyperfine structure of an NV center depends on its surrounding electric field. This dependence is well understood theoretically, and was exploited by Iwasaki and co-workers: detecting changes in an NV center's hyperfine structure enabled them to obtain values for the local electric field. A major advantage of this approach is that it allows monitoring the field within the material -- not just at the surface, for which methods had already been developed.

Optically-detected magnetic resonance

For probing the nuclear hyperfine structure of an NV center in the bulk of the diamond-based device, Iwasaki and colleagues employed optically detected magnetic resonance (ODMR): by irradiating the sample with laser light, the NV center was optically excited, after which the magnetic resonance spectrum could be recorded. An electric field makes the ODMR resonance split; the experimentally detected split width provides a measure for the electric field.

###

Acknowledgment

This work was supported by a fund from Core Research Evolutionary Science and Technology (CREST) of the Japan Science and Technology Agency (JST).

Media Contact

Emiko Kawaguchi
media@jim.titech.ac.jp
81-357-342-975

http://www.titech.ac.jp/english/index.html 

Emiko Kawaguchi | EurekAlert!

More articles from Materials Sciences:

nachricht A materials scientist’s dream come true
21.08.2018 | Friedrich-Alexander-Universität Erlangen-Nürnberg

nachricht Novel sensors could enable smarter textiles
17.08.2018 | University of Delaware

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries

There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.

The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

A paper battery powered by bacteria

21.08.2018 | Power and Electrical Engineering

Protein interaction helps Yersinia cause disease

21.08.2018 | Life Sciences

Biosensor allows real-time oxygen monitoring for 'organs-on-a-chip'

21.08.2018 | Medical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>