2025/12/09 by Dill, Joseph E., Wei, Xianzhi, Yu, Changkai +6
Engineering · Physics and Astronomy · #FOS: Physical sciences #GaN-based semiconductor devices and materials #Materials Science (cond-mat.mtrl-sci) #Plasmonic and Surface Plasmon Research #Semiconductor Quantum Structures and Devices
paper · doi:10.48550/arxiv.2512.08871
openalex publication_date 2025/12/09 · openalex created_date 2025/12/11 · openalex updated_date 2026/07/28
Ohmic contacts to high (>70%) Al content n-type AlxGa1-xN ultra-wide bandgap semiconductor layers in nitride electronic and photonic devices are typically fabricated by a lift-off process and high temperature (>700^∘C) thermal alloying. These conditions often result in significant structural deformations of the fabricated structures and impose a harsh thermal budget on all other aspects of the device. Here, we report the fabrication of non-alloyed as-deposited ohmic contacts to 71% n+AlGaN (Eg∼5.4~eV) with a free carrier concentration of roughly 7× 1019~cm-3 and a resistivity of 4 - 5.5 mΩcm (among the lowest reported for Al0.71Ga0.29N) with linear I-V characteristics and a contact resistivity of ρc=(4.4±1.0)×10-4~Ωcm2 (measured at zero voltage). Contacts with this quality are formed by two separate fabrication schemes: (i) metal-first patterning, and (ii) lift-off with an oxygen asher descum prior to metal deposition. Given the low threading dislocation density in the single-crystal AlN substrate used for epitaxy, the smooth morphology of the contacted epitaxial surface, and the non-alloyed nature of the contacts, this contact resistivity is attributed purely to thermionic field emission through the metal-semiconductor junction. Contact resistivity extraction at low current injection enables us to model these results using a thermionic field-emission model of contact resistivity, yielding a barrier height for Ti/Al0.71Ga0.29N of (0.81±0.02) eV.