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Power Nitride Doping Innovation Offers Devices Enabling SWITCHES

The projects that comprise ARPA-E's PNDIODES (Power Nitride Doping Innovation Offers Devices Enabling SWITCHES) program seek to develop transformational advances in the process of selective area doping in the wide-bandgap (WBG) semiconductor, gallium nitride (GaN), and its alloys. Wide-bandgap semiconductors have applications similar to today's popular semiconductors, such as silicon and gallium arsenide, but with properties that allow them to operate at much higher voltages, frequencies and temperatures than these traditional materials. These qualities inherent to WBGs stand to enable high-power, high-performance power conversion hardware for a broad range of applications, including consumer electronics, the electricity grid, power supplies, solar and wind power, automotive, ship propulsion, and aerospace. The doping process, the challenge central to the PNDIODES program, consists of adding a specific impurity to a semiconductor to change its electrical properties--altering its physical makeup to achieve performance characteristics that are useful for electronics. Developing a reliable and usable doping process that can be applied to specific regions of the semiconductor gallium nitride and its alloys remains an important obstacle in the fabrication of power electronics devices using this technology. The PNDIODES program is an extension of ARPA-E's SWITCHES (Strategies for Wide-Bandgap, Inexpensive Transistors for Controlling High-Efficiency Systems) program, seeking to fill technological gaps in the area of selective area doping, further advancing the field by addressing the problem of producing sufficiently high quality and reliably doped regions in GaN and its alloys to create viable high-power, high-performance transistors.
For a detailed technical overview about this program, please click here.    

Adroit Materials Inc

Selective Area Doping for Nitride Power Devices

Adroit Materials will develop a gallium nitride (GaN) selective area doping process to enable high-performance, reliable GaN-based, high-power switches which are promising candidates for future high efficiency, high power electronic applications.. Specifically, doping capabilities that allow for the creation of localized doped regions must be developed for GaN in order to reach its full potential as a power electronics semiconductor. Adroit's process will focus on implantation of magnesium ions and an innovative high temperature, high pressure activation anneal, or heat treatment, process to remove implantation damage and control performance-reducing defects. By developing an in-depth understanding of the ion implantation doping process, the team will be able to demonstrate usable and reliable planar and embedded p-n junctions, the principal building block of modern electronic components like transistors.

Arizona State University

Effective Selective Area Doping for GaN Vertical Power Transistors Enabled by Innovative Materials Engineering

Arizona State University (ASU) proposes a comprehensive project to advance fundamental knowledge in the selective area doping of GaN using selective regrowth of gallium nitride (GaN) materials. This will lead to the development of high-performance GaN vertical power transistors. The ASU team aims to develop a better mechanistic understanding of these fundamental materials issues, by focusing on three broad areas. First, they will use powerful characterization methods to study fundamental materials properties such as defects, surface states, and investigate possible materials degradation mechanisms. Next, they will develop innovative epitaxial growth and fabrication processes such as Atomic Layer Etching and novel surface passivations, to tackle the materials engineering challenges related to selective area doping for GaN p-n junctions. Finally, they will apply their research to demonstrate randomly placed, reliable, contactable p-n junctions for GaN vertical power devices. If successful, this project will provide a path towards high efficiency, high power, small form factor, and high thermal performance GaN vertical power devices.


Laser Spike Anneal Technology for the Activation of Implanted Dopants in Gallium Nitride

Advanced doping methods are required to realize the potential of gallium nitride (GaN)-based devices for future high efficiency, high power applications. Ion implantation is a doping process used in other semiconductor materials such as Si and GaAs but has been difficult to use in GaN due to the limited ability to perform a damage recovery anneal in GaN. JR2J will develop an innovative laser spike annealing technique to activate implanted dopants in GaN. Laser spike annealing is a high-temperature (above 1300 ºC) heat treatment technique that activates the dopants in GaN and repairs damage done during the implantation process. By keeping the laser spike duration very short (0.1-100 milliseconds), the technique is hypothesized to be short enough to avoid degradation of the GaN lattice itself. There are commercially available laser spike annealing systems, typically used in Si-based processes, which should be able to be adapted to annealing GaN substrates with small modifications. If the proof of concept is achieved, this could provide a fast road to commercialization.

Lawrence Livermore National Laboratory

Magnesium Diffusion Doping of GaN

Livermore National Laboratory (LLNL) will advance GaN device processing knowledge to enable production of GaN devices with higher speed and power at a lower cost. Using a selective area p-type doping process to move the device architecture from a lateral to a vertical configuration makes the lower cost possible. LLNL has previously demonstrated solid-state diffusion of magnesium (Mg) into GaN at temperatures under 1000ºC through a Gallidation Assisted Impurity Diffusion (GAID) process. In the GAID process, an Mg source layer is deposited in contact with the GaN followed by a capping layer of a metal that reacts with GaN at moderate temperatures to form gallides. The closeness of this capping layer with the GaN allows reaction with the underlying GaN, removing gallium from the lattice where it is replaced with Mg. This results in Mg incorporation within the GaN lattice and p-type doping. LLNL will evaluate various Mg sources, capping layers, and diffusion conditions for the GAID process and determine the relationship among source type, thickness, and capping layer on the resulting p-type doping concentration.

Sandia National Laboratory

High Voltage Re-grown GaN P-N Diodes Enabled by Defect and Doping Control

Vertical transistors based on bulk gallium nitride (GaN) have emerged as promising candidates for future high efficiency, high power applications. However, they have been plagued by poor electrical performance attributed to the existing selective doping processes. Sandia National Laboratories will develop patterned epitaxial regrowth of GaN as a selective area doping processes to fabricate diodes with electronic performance equivalent to as-grown state-of-the-art GaN diodes. The team's research will provide a better understanding of which particular defects resulting from impurities and etch damage during the epitaxial regrowth process limit device performance, how those defects specifically impact the junction electronic properties, and ultimately how to control and mitigate the defects. The improved mechanistic understanding developed under the project will help the team design specific approaches to controlling impurity contamination and defect incorporation at regrowth interfaces and include development of in-chamber cleans and regrowth initiation processes to recover a high-quality epitaxial surfaces immediately prior to crystal regrowth.

SUNY Polytechnic

Demonstration of PN-junctions by Ion implantation techniques for GaN (DOPING-GaN)

The Research Foundation for the State University of New York (SUNY), on behalf of SUNY Polytechnic University, will develop innovative doping process technologies for gallium nitride (GaN) vertical power devices to realize the potential of GaN-based devices for future high efficiency, high power applications. SUNY Polytechnic's proposed research will focus on ion implantation to enable the creation of localized doping that is necessary for fabricating GaN vertical power devices. Ion implantation is a doping process used in other semiconductor materials such as Si and GaAs but has been difficult to use in GaN due to the limited ability to perform high temperature heat treatments or anneals needed to activate the implanted dopants and repair the damage caused by implantation. The team will develop new annealing techniques to activate magnesium or silicon implanted in GaN to build p-n junctions, the principal building block of modern electronic components like transistors. High temperature anneals will be performed using an innovative gyrotron beam technique (a high-power vacuum tube that generates millimeter-length electromagnetic waves) and an aluminum nitride cap. Central to the team's project is understanding the impact of implantation on the microstructural properties of the GaN material and effects on performance.

University of Missouri

High quality GaN FETs through transmutation doping and low temperature processing

The University of Missouri will develop neutron transmutation doping of GaN to fabricate uniform heavily doped n-type GaN wafers. GaN has long been proposed as a superior material for power electronic devices due to the intrinsic material advantages such as greater breakdown voltages and greater stability. Unfortunately, the fabrication of GaN wafers with uniform and high levels of dopants is challenging due to a lack of sufficient control during the existing crystal growth methods. The neutron transmutation doping process, which consists of exposing GaN wafers to neutron radiation to create a stable network of the dopant germanium within the GaN wafer, allows for a greater degree of precision and results in a high level, uniform doping concentrations across the wafer. With this method, repeatable production of high quality GaN substrates may be achieved. Specific innovations in this proposal concern an in-depth study of neutron transmission doping and a characterization of the resulting wafer, including analyzing resistivity, dopant concentration, unwanted impurities, and damage to the GaN lattice.

Yale University


Yale University will conduct a comprehensive investigation to overcome the barriers in selective area doping of gallium nitride (GaN) through an epitaxial regrowth process for high-performance, reliable GaN vertical transistors. Transistors based on GaN have emerged as promising candidates for future high efficiency, high power applications, but they have been plagued by poor electrical performance attributed to the existing selective doping processes. The team will demonstrate vertical GaN diodes through a selective area regrowth processes with performance similar to those made using current in situ techniques, which are non-selective and therefore less flexible. Key innovations in this project will be to use three-dimensional nanoscale characterizations to understand the regrowth interface formation at the nano scale, and to apply atomic-level manipulation to control impurities, and suppress extrinsic and intrinsic defects at the selective area regrowth interface. This will enable the electronic characteristics of the selective area growth p-n junction active region to be customized allowing for high performance GaN vertical transistors. The successful production of reliable and high-performance GaN vertical transistors on bulk substrates will be transformative to many mid-voltage applications including photovoltaic inverters, motor control, and hybrid automotive.
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