| AVS 63rd International Symposium & Exhibition | |
| Electronic Materials and Photonics | Monday Sessions |
| Session EM-MoA |
| Session: | Surface and Interface Challenges in Wide Bandgap Materials |
| Presenter: | Travis Anderson, U.S. Naval Research Laboratory |
| Authors: | D.I. Shahin, University of Maryland College Park T.J. Anderson, U.S. Naval Research Laboratory V.D. Wheeler, U.S. Naval Research Laboratory M.J. Tadjer, U.S. Naval Research Laboratory A.D. Koehler, U.S. Naval Research Laboratory K. Hobart, U.S. Naval Research Laboratory C.R. Eddy, Jr., U.S. Naval Research Laboratory F. Kub, U.S. Naval Research Laboratory A. Christou, University of Maryland College Park |
| Correspondent: | Click to Email |
AlGaN/GaN high electron mobility transistors (HEMTs) are useful devices for next-generation RF and power electronics systems1,2. Traditional Ni-based Schottky gates in these devices have been shown to degrade when subjected to electrical stress, thermal stress, and radiation due to Ni migration into adjacent metal or semiconductor layers3,4. The instability of these Ni-based gates limits device reliability, rendering the search for replacement gate materials that are electrically- and thermally-stable a topic of tremendous importance. Of the transition metal nitrides, TiN is a particularly promising material, due to its near-metallic conductivity, suitable Schottky barrier heights and ideality factors on GaN and AlGaN, and high temperature stability. This work investigates the performance of atomic layer deposited (ALD) TiN gates and directly compares them to traditional Ni/Au gates.
ALD TiN gates (75nm thick) were deposited on AlGaN/GaN HEMTs in an Oxford FlexAL system at 350°C using Tetrakis(dimethyamido)titanium (TDMA-Ti)and an N2/H2 plasma as precursors. Devices with TiN gates exhibited improved static and dynamic on-state characteristics compared to the identical Ni/Au-gated HEMTs. Reverse bias gate stressing indicated a higher critical voltage (VgsTiN = -210V, VgsNi/Au = -120V) and a higher breakdown voltage (VgsTiN = -270 ± 10 V, VgsNi/Au = 240 ± 30V)for the TiN gates. Furthermore, the TiN gates exhibited a decrease in reverse leakage current after stressing indicating enhanced stability. Gate thermal stability was assessed through sequential device annealing from 400-800C in 100C increments. The TiN gated devices exhibited stable DC operation up to 800°C, while the Ni/Au gates showed significant degradation after annealing above 500°C and failed above 700°C. This suggests that ALD TiN gates are a strong candidate for reliable HEMT gate metallization and other applications where increased stability is required at higher temperatures.
1 R.S. Pengelly, et al., IEEE Trans. Microwave Theory Tech.60 [6], 1764 (2012).
2 S.J. Pearton, et al., J. Vac. Sci. Technol. A 31 [5], 050801 (2013).
3 Y.H. Choi, et al., Materi. Res. Soc. Symp. Proc.1167, 1167-O05-06 (2009).
4 A.D. Koehler, et al., IEEE Elect. Dev. Lett.35 [12], 1194 (2014).