Evaluation of Low-Temperature Saturation Velocity in &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$\beta$ &lt;/tex-math&gt; &lt;/inline-formula&gt;-(AlxGa1–x)2O3/Ga2O3 Modulation-Doped Field-Effect Transistors

Yuewei Zhang,Chandan Joishi,Steven A Ringel,Joe Mcglone,Aaron R Arehart,Wenyuan Sun,Zhanbo Xia,Siddharth Rajan

doi:10.1109/ted.2018.2889573

Abstract

We report on the high-field transport characteristics and saturation velocity in a modulation-doped β-(Al x Ga 1-x ) 2 O 3 /Ga 2 O 3 heterostructure. The formation of a 2-D electron gas (2DEG) in the modulation-doped structure was confirmed from the Hall measurements, and the 2DEG channel mobility increased from 143 cm 2 /V·s at room temperature to 1520 cm 2 /V·s at 50 K. The high electron mobility at 50 K made it feasible to achieve velocity saturation inside the channel. The saturation velocity was estimated based on both pulsed current-voltage measurements and smallsignal radio frequency (RF) measurements. The measured velocity-field profile suggested a saturation velocity above 1.1 x 10 7 cm/s at 50 K. The small-signal RF characteristics were measured for the fabricated modulation-doped field-effect transistors with a Pt-based Schottky contact. The current gain cutoff frequency (f t ) and maximum oscillation frequency (f max ) showed significant increases from 4.0/11.8GHz at room temperature to 17.4/40.8GHz at 50 K for the device with gate length of L G = 0.61 μm. The analysis of the low temperature f t based on device simulations indicated a peak velocity of 1.2 x 10 7 cm/s. The three-terminal off-state breakdown measurement further suggested an average breakdown field of 3.22 MV/cm. The high saturation velocity and high breakdown field in β-Ga 2 O 3 make it a promising candidate for high-power and high-frequency device applications.

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