Low resistive Au-free, Ta-based, recessed ohmic contacts to InAlN/AlN/GaN heterostructures. (21st September 2015)

• Record Type: Journal Article
• Authors: Bergsten, J; Malmros, A; Tordjman, M; Gamarra, P; Lacam, C; di Forte-Poisson, M-A; Rorsman, N
• Is Part Of: Semiconductor science and technology. Volume 30:Number 10(2015:Oct.)
• Publication Date: 2015-09-21
• Subjects: Au-free -- ohmic contact -- recess etch -- InAlN -- high electron mobility transistor -- GaN; Semiconductors -- Periodicals; 621.38152
• DOI: 10.1088/0268-1242/30/10/105034
• Languages: English
• ISSNs: 0268-1242

Abstract

Abstract: The formation of recess etched Au-free ohmic contacts to an InAlN/AlN/GaN heterostructure is investigated. A Ta/Al/Ta metal stack is used to produce contacts with contact resistance ( R c ) as low as 0.14 Ω mm. It is found that R c decreases with increasing recess depth until the InAlN barrier is completely removed. For even deeper recesses R c remains low but requires annealing at higher temperatures for contact formation. The lowest R c is found for contacts where the recess etch has stopped just above the 2D electron gas channel. At this depth the contacts are also found to be less sensitive to other process parameters, such as anneal duration and temperature. An optimum bottom Ta layer thickness of 5–10 nm is found. Two reliability experiments preliminary confirm the stability of the recessed contacts.