Low-resistivity Ohmic Contacts for Extreme Bandgap Nitride Semiconductors and their Digital Alloys
Abstract
0,Extreme Bandgap (EBG) III-Nitride semiconductors materials with bandgaps more than 5 eV, offer unique opportunities for miniaturizat,ion of power systems while providing unrivaled thermal capability, voltage capacity and reliability (owing to lower leakage current/,p, making it approximately a factor of 2-4 higher for EBG Aluminum Gallium Nitride than that for Gallium Nitride and Silicon Carbide, (wide bandgap semiconductors). This makes their Baliga Figure of Merit (BFOM) at room temperature a factor of 2-4 higher than wide,bandgap semiconductors as well. For operation temperatures at 250 C, this advantage becomes a factor of 6 because the temperature d,riven mobility reduction in EBG materials is not as severe as that for WBG materials. The forecasted US Navy Power Electronic Power, Distribution Systems (PEPDS) plan contains several lofty high voltage AC busses constructed from Navy integrated Power Electronics,Building Blocks (iPEBB) ranging from 1000V modules to 13-20 KV modules. Extreme bandgap semiconductors, such as Aluminum Gallium Nit,ride which were pioneered under the ?New Paradigm? MURI led by Dr. Sam Graham and administered by Lynn Peterson provide a unique opp,ortunity to address the above-mentioned issues. Their higher breakdown field, better thermal conductivity combined with new manufact,uring methods have led to quality improvements that now make feasible new high voltage device opportunities. For the first time, th,e combination of high critical field, the key parameter determining safe operational voltage, and thick epitaxial films enabled by n,ew manufacturing advances, combine to facilitate practical single device solutions for high voltage iPEBBs all the way up to (and po,ssibly exceeding) 20KV. Thus, targeted 100 MW systems based on 20KV iPEBBs could be cost effectively implemented.But there remains a,n important challenge in this newly emerging scientific arena: limitation of the current carrying capability, which is a result of h,igh contact resistivity. The lowest contact resistivities achievable to date led to impressive device demonstrations but are still,too high. The newness of the EBG III-Nitride field has resulted in immaturity of the contact technology, requiring new scientific,solutions, and further understanding of present bottlenecks. Our independent focused program described here addresses the contact bo,ttleneck. In addition to high-voltage power electronics, such low-resistance ohmic contacts will also improve the performance of hi,gh temperature electronics, UVC Solar blind sensors, UVC lasers and high-power rf-electronics. To overcome this electrical current l,ductor junctions, feeding off of successful past approaches while introducing new alternatives;2) Combine metal-semiconductor contac,ts with growth-enabled new structures including polarization graded and new dopant enhanced polarization graded structures; 3) Intro,duce lateral engineered contacts using spread current channels; and 4) Use quantum mechanical methods such as tunnel junctions to co,ntact extreme bandgap energy devices in ways prior devices could not feasibly achieve.The UofSC program will have close collaboratio,n with Prof. Alan Doolittle at Georgia Tech and Prof. Suzanne Mohney at Penn State. This collaboration will facilitate the combinat,ion of MBE/MOCVD growth techniques and the excellent ohmic contact analysis capabilities to increase the chances of success. As evi,denced from the current ONR MURI program, such collaboration and sharing of resources is highly cost beneficial and accelerates the,program success.?Approved for Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 04, 2022
- Source ID
- N000142312010
Entities
People
- Asif Khan
Organizations
- Office of Naval Research
- United States Navy
- University of South Carolina