• Kirste, Ronny
• Breckenridge, M. Hayden
• Mita, Seiji
• Pavlidis, Spyridon
• Kohn, Erhard
• Dycus, J. Houston
• Rathkanthiwar, Shashwat
• Bagheri, Pegah
• Reddy, Pramod
• Dangi, Saroj
• Sengupta, Rohan
• Collazo, Ramón

Abstract

<jats:p> The ultra-wide bandgap of Al-rich AlGaN is expected to support a significantly larger breakdown field compared to GaN, but the reported performance thus far has been limited by the use of foreign substrates. In this Letter, the material and electrical properties of Al<jats:sub>0.85</jats:sub>Ga<jats:sub>0.15</jats:sub>N/Al<jats:sub>0.6</jats:sub>Ga<jats:sub>0.4</jats:sub>N high electron mobility transistors (HEMT) grown on a 2-in. single crystal AlN substrate are investigated, and it is demonstrated that native AlN substrates unlock the potential for Al-rich AlGaN to sustain large fields in such devices. We further study how Ohmic contacts made directly to a Si-doped channel layer reduce the knee voltage and increase the output current density. High-quality AlGaN growth is confirmed via scanning transmission electron microscopy, which also reveals the absence of metal penetration at the Ohmic contact interface and is in contrast to established GaN HEMT technology. Two-terminal mesa breakdown characteristics with 1.3  μm separation possess a record-high breakdown field strength of ∼11.5 MV/cm for an undoped Al<jats:sub>0.6</jats:sub>Ga<jats:sub>0.4</jats:sub>N-channel layer. The breakdown voltages for three-terminal devices measured with gate-drain distances of 4 and 9  μm are 850 and 1500 V, respectively. </jats:p>

Topics

• density
• impedance spectroscopy
• single crystal
• mobility
• strength
• transmission electron microscopy
• current density