High-Current Perovskite Oxide BaTiO<sub>3</sub>/BaSnO<sub>3</sub> Heterostructure Field Effect Transistors
Junao Cheng, Caiyu Wang, Christopher R. Freeze, Omor Shoron, Nick Combs, Hao Yang, Nidhin Kurian Kalarickal, Zhanbo Xia, Susanne Stemmer, Siddharth Rajan, Wu Lu
Abstract
High-current molecular beam epitaxial perovskite oxide semiconductor BaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /BaSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> heterostructure field effect transistors on SrTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> substrates were developed. Record high current density of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> = 406.7 mA/mm, maximum transconductance gm = 72.3 mS/mm were achieved in a field effect transistor with gate length L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> = 0.64 μm, and source-drain spacing L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sd</sub> = 3.5 μm. The device has a low threshold voltage of V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> = -4.5 V and the capability to modulate 5.7× 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> electron density in the BaSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> channel. The high channel current and gate modulation efficiency are attributed to the high mobility and charge density in the BaSnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> channel and the utilization of high-k BaTiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (e is in the range of 425 and 387 as the electric field increases from 46 to 85 kV/cm) layer as the gate dielectric for charge modulation. Though the device suffers from low current ON/OFF ratio and a large subthreshold swing due to the gate leakage resulted from threading dislocations, this work demonstrates the great potential of perovskite semiconductors for electronic device applications.