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Magnesium Diffusion Doping of GaN

Lawrence Livermore National Laboratory (LLNL)
Program: 
ARPA-E Award: 
$500,000
Location: 
Livermore, CA
Project Term: 
09/01/2019 to 08/31/2020
Project Status: 
ACTIVE
Technical Categories: 
Critical Need: 

Electricity generation currently accounts for ~40% of primary energy consumption in the U.S. and continues to be the fastest growing form of end-use energy. Power electronics are responsible for controlling and converting electrical power to provide optimal conditions for transmission, distribution, and load-side consumption. By 2030 as much as 80% of all electricity could pass through some form of power electronics. Applications for power electronics are widespread and include uses in power supplies, motor drives, grid applications, data centers, and distributed energy resources. Today, most power electronics are based on silicon semiconductor devices that have reached their efficiency limits at high power and frequency, due to the material limitations of silicon. Wide-bandgap (WBG) semiconductors such as gallium nitride (GaN) have superior electrical conductivity, breakdown properties, and switching speed. This allows for power converters with much improved efficiencies over silicon - while also dramatically reducing system size, weight, and form factor. Power semiconductor devices overwhelmingly use vertical architectures to realize higher breakdown voltages (>1200V) and current levels, without having to enlarge chip size. The vertical architectures require the ability to add specific impurities to selected regions of a semiconductor to produce negative (n-type) and positive (p-type) electrical conduction, a process called doping. Currently, no doping process exists to form selective p-type regions in GaN. This is the major barrier to realization of GaN based vertical power electronic devices. The development of a selective p-type doping process will enable vertical GaN device architectures and unlock the potential of using the WBG semiconductor GaN in power electronics.

Project Innovation + Advantages: 

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.

Potential Impact: 

If successful, PNDIODES projects will enable further development of a new class of power converters suitable in a broad range of application areas including automotive, industrial, residential, transportation (rail & ship), aerospace, and utilities.

Security: 

More energy efficient power electronics could improve the efficiency of the U.S. power sector. They could also significantly improve the reliability and security of the electrical grid.

Environment: 

More efficient power use may help reduce power-related emissions. Low-cost and highly efficient power electronics could also lead to increased adoption of electric vehicles and greater integration of renewable power sources.

Economy: 

Improved power electronics could yield a significant reduction in U.S. electricity consumption, saving American families and businesses money on their power bills.

Contacts
ARPA-E Program Director: 
Dr. Isik Kizilyalli
Project Contact: 
Voss Lars
Partners
Yale University
Release Date: 
6/14/2017