industry news
Subscribe Now

Plumbing the Depths: Defect Distribution in Ion-Implanted SiC Diodes

Researchers reveal that aluminum implantation doping in p-type bipolar semiconductors creates defects many layers deeper than the implantation site
Introducing a vertical arrangement of n and p layers into the drift layer of semiconductors to enable bipolar operation is a way around the ‘unipolar limit’ problem in semiconductors. But defect generation during the fabrication of such devices is a matter of concern. Researchers have examined the depth and distribution of defects formed by aluminum ion implantation in silicon carbide bipolar diodes to identify ways to induce efficient conductivity modulation.
Silicon carbide (SiC) unipolar semiconductors are in wide commercial use, but their operations are limited by a trade-off relationship between breakdown voltage and specific resistance of the drift layer, or specific on-resistance. Including a super junction structure, which refers to an arrangement of n and p layers in trenches in the drift layer, or enabling bipolar operation in the device, provides a way to overcome this unipolar limit. Bipolar operation brings about a large decrease in on-resistance by inducing a conductivity modulation in the drift layer. But bipolar operation is not without its disadvantages. Conduction and switching losses in bipolar devices need to be carefully balanced.
P-type contact layers in semiconductors are generally formed via aluminum (Al) doping. Al doping can be achieved in two ways – epitaxial or ion implantation. Epitaxial growth involves the layer by layer deposition of semiconductor materials on a substrate, whereas ion implantation entails bombarding the semiconductor layers with high energy charged particles. But ion implantation leads to the formation of defects deep in the semiconductor layers, which could have a critical effect on conductivity modulation.
In a recent study published in Physica Status Solidi (b)researchers from Japan investigated the depth distribution of defects in SiC bipolar diodes that were formed by Al doping. “Our findings will help with the optimum design of SiC power devices, which will soon be employed in electric vehicles, trains etc. These results will ultimately help improve the performance, as well as the size and energy consumption of traction systems in vehicles and trains,” says Associate Professor Dr. Masashi Kato of Nagoya Institute of Technology, who led the study.
To study the depth distribution of defects, the research team fabricated two SiC PiN diodes with Al doped p-layers, one through epitaxial growth and the other through ion implantation. They then studied the distribution of defects in both diodes using conventional ‘deep level transient spectroscopy’ (DLTS) and characterized its properties using cathodoluminescence (CL). They found that p-type layer deposition by epitaxial growth did not cause damage in the adjacent n-type layers, but that the growth showed slight instability that led to the formation of deep level defects. The specific on-resistance of this diode was also low, thanks to the effects of conductivity modulation.
For the diode formed by ion implantation, however, the researchers found that Al doping achieved a high specific on-resistance without influencing conductivity modulation. Moreover, the researchers observed that the defects in the semiconductor device penetrated to a minimum of 20 µm from the implantation region. “Our study shows that the ion implantation in SiC bipolar devices need to be processed at least 20 µm away from the active regions,” explains Dr. Kato.
The low power consumption of SiC power devices mean that they will be essential in the future as climate change increases and the fossil fuel energy crisis worsens. Improving semiconductor technology rapidly so that it can take its rightful place on the world stage is of paramount importance. With strong results like this to inform future research and manufacturing, we may realize this future sooner than expected!
Reference
Title of original paper: Depth distribution of defects in SiC PiN diodes formed using ion implantation or epitaxial growth
Journal: Physica Status Solidi (b)
About Nagoya Institute of Technology, Japan
Nagoya Institute of Technology (NITech) is a respected engineering institute located in Nagoya, Japan. Established in 1949, the university aims to create a better society by providing global education and conducting cutting-edge research in various fields of science and technology. To this end, NITech provides a nurturing environment for students, teachers, and academicians to help them convert scientific skills into practical applications. Having recently established new departments and the “Creative Engineering Program,” a 6-year integrated undergraduate and graduate course, NITech strives to continually grow as a university. With a mission to “conduct education and research with pride and sincerity, in order to contribute to society,” NITech actively undertakes a wide range of research from basic to applied science.
About Professor Masashi Kato from Nagoya Institute of Technology, Japan
Dr. Masashi Kato graduated in Electrical and Computer Engineering from Nagoya Institute of Technology in 1998 and then proceeded to obtain both a Master’s (2000) and a PhD (2003) in the same field there. He is currently an Associate Professor of Semiconductor Physics and has authored around 100 publications in the course of his career. His field of expertise and research interests lie within electronic/electric materials and device-related chemistry, and he has been a member of The Japan Society of Applied Physics for over two decades.
Funding information:
This study has been supported by SIP (Strategic Innovation Promotion Program) of the Council for Science, Technology and Innovation [Next generation power electronics / Integrated research and development of SiC for next generation power electronics] (management corporation: NEDO).

Leave a Reply

featured blogs
Dec 2, 2021
Another six months have passed since we posted our last blog on Layout Verification. We are now happy to introduce some new videos around this topic especially around the next generation parasitic... [[ Click on the title to access the full blog on the Cadence Community site...
Dec 1, 2021
We discuss semiconductor lithography and the importance of women in engineering with Mariya Braylovska, Director of R&D for Custom Design & Manufacturing. The post Q&A with Mariya Braylovska, R&D Director, on the Joy of Solving Technical Challenges with a...
Nov 30, 2021
Have you ever wondered why Bill is a common nickname for William and Dick is a common nickname for Richard?...
Nov 8, 2021
Intel® FPGA Technology Day (IFTD) is a free four-day event that will be hosted virtually across the globe in North America, China, Japan, EMEA, and Asia Pacific from December 6-9, 2021. The theme of IFTD 2021 is 'Accelerating a Smart and Connected World.' This virtual event ...

featured video

Architecture All Access: Modern FPGA Architecture

Sponsored by Intel

In this 20-minute video, Intel Fellow Prakash Iyer takes you on a journey within the architecture of an FPGA, starting with simple logic gates and then moving up through architecture, design, and applications. Along the way, he answers many questions you might have about FPGAs, even if you’ve worked with FPGAs for years.

Click here for more information

featured paper

Extending Battery Life in Medical Wearable Devices

Sponsored by Analog Devices

Portable medical equipment requires both long battery life and small form factor to ensure successful patient use and positive medical outcomes. ADI’s MAX16164, nanoPower on/off controller, addresses both longevity and portability while offering design flexibility with programmable sleep time.

Click to read more

featured chalk talk

Tame the SiC Beast - Unleash the Full Capacity of Silicon Carbide

Sponsored by Mouser Electronics and Microchip

Wide band gap materials such as silicon carbide are revolutionizing the power industry. At the same time, they can also introduce byproducts including overheating, short circuits and over voltage. The question remains: how can we use silicon carbide without those headache-inducing side effects? In this episode of Chalk Talk, Amelia Dalton chats with Rob Weber from Microchip about Microchip’s patented augmented switching technology can make those silicon carbide side effects a thing of the past while reducing our switching losses up to 50% and accelerating our time to market as well.

Click here for more information about the Microsemi / Microchip AgileSwitch® ASDAK+ Augmented Switching™ Dev Kit